Determine if a string is numeric: Difference between revisions

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Latest revision as of 08:41, 12 March 2024

Task

Create a boolean function which takes in a string and tells whether it is a numeric string (floating point and negative numbers included) in the syntax the language uses for numeric literals or numbers converted from strings.

Other tasks related to string operations:

Metrics

Counting

Remove/replace

Anagrams/Derangements/shuffling

Find/Search/Determine

Formatting

Song lyrics/poems/Mad Libs/phrases

Tokenize

Sequences

6502 Assembly

For this program, a valid numeric string literal consists of only numbers (ascii $30-$39), up to one leading minus sign, and no more than one decimal point. Anything else, including the null string, is considered non-numeric.

Macros used (VASM syntax):


macro loadpair,regs,addr
	lda #<\addr
	sta \regs
	lda #>\addr
	sta \regs+1
endm

macro pushY
	tya
	pha
endm

macro popY
	pla
	tay
endm

The code:

*=$0801
	db $0E,$08,$0A,$00,$9E,$20,$28,$32,$30,$36,$34,$29,$00,$00,$00  ;required init code on commodore 64 floppy disks
*=$0810

	lda #$0e
	jsr chrout ;required for my printing routine to work.

z_HL equ $02
z_L  equ $02
z_H  equ $03
z_B  equ $04
	
	
	
	loadpair z_HL,TestString0
	jsr isStringNumeric
	
	loadpair z_HL,TestString1
	jsr isStringNumeric
	
	loadpair z_HL,TestString2
	jsr isStringNumeric
	
	loadpair z_HL,TestString3
	jsr isStringNumeric	

	loadpair z_HL,TestString4
	jsr isStringNumeric
	
	loadpair z_HL,TestString5
	jsr isStringNumeric
	
	loadpair z_HL,TestString6
	jsr isStringNumeric
	
	loadpair z_HL,TestString7
	jsr isStringNumeric	
	
	loadpair z_HL,TestString8
	jsr isStringNumeric	
	rts				;return to basic

isStringNumeric:
; input: z_HL = source address
	pushY
		ldy #0
		sty z_B		;our tally for decimal points
		
checkFirstChar:
		lda (z_HL),y
		beq notNumeric			;a null string is not a valid number!
		cmp #'-'
		beq isNegative_OK
		cmp #'.'
		beq isFloat_OK
		and #$30
		cmp #$30
		beq isNumeral_OK
		;else, is not numeric
notNumeric:
	popY
	jsr PrintString_TextScreen	;prints what's already in z_HL
	jsr NewLine	
	loadpair z_HL,isStringNumeric_Fail
	jsr PrintString_TextScreen
	jsr NewLine
	jmp NewLine
	;rts
isNegative_OK:
isNumeral_OK:
		iny
		jmp loop_isStringNumeric
isFloat_OK:
		iny
		inc z_B
loop_isStringNumeric:
		lda (z_HL),y
		beq Terminated_isStringNumeric
		cmp #'.'
		beq CheckIfDecimalAlreadyOccurred
		and #$30
		cmp #$30
		bne notNumeric
loop_overhead_isStringNumeric:
		iny
		jmp loop_isStringNumeric
		
CheckIfDecimalAlreadyOccurred:
		lda z_B
		bne notNumeric
		inc z_B
		jmp loop_overhead_isStringNumeric
		
Terminated_isStringNumeric:
;if we got this far the string is numeric.
	popY
	jsr PrintString_TextScreen	;prints what's already in z_HL
	jsr NewLine	
	loadpair z_HL,isStringNumeric_Pass
	jsr PrintString_TextScreen
	jsr NewLine
	jmp NewLine
	;rts
	
isStringNumeric_Pass:
	db "IS NUMERIC",0
isStringNumeric_Fail:
	db "IS NOT NUMERIC",0
	
TestString0:
	db 0
TestString1:
	db "123",0
TestString2:
	db "-30",0
TestString3:
	db "123.45",0
TestString4:
	db "-123.45",0
TestString5:
	db "ABCDE",0
TestString6:
	db "-34-5",0
TestString7:
	db "1.000.000",0
TestString8:
	db ".23456",0

Output:

ready.
load"*",8,1:

searching for *
loading
ready.
run

IS NOT NUMERIC

123
IS NUMERIC

-30
IS NUMERIC

123.45
IS NUMERIC

-123.45
IS NUMERIC

ABCDE
IS NOT NUMERIC

-34-5
IS NOT NUMERIC

1.000.000
IS NOT NUMERIC

.23456
IS NUMERIC

ready.

8th

: number? >n >kind ns:n n:= ;

AArch64 Assembly

Works with: as version Raspberry Pi 3B version Buster 64 bits

/* ARM assembly Raspberry PI  */
/*  program strNumber.s   */


/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"

.equ BUFFERSIZE,          100


/* Initialized data */
.data
szMessNum: .asciz "Enter number : \n"

szMessError:            .asciz "String is not a number !!!\n"
szMessInteger:          .asciz "String is a integer.\n"
szMessFloat:            .asciz "String is a float.\n"
szMessFloatExp:         .asciz "String is a float with exposant.\n"
szCarriageReturn:       .asciz "\n"

/* UnInitialized data */
.bss 
sBuffer:              .skip BUFFERSIZE

/*  code section */
.text
.global main 
main: 

loop:
    ldr x0,qAdrszMessNum
    bl affichageMess
    mov x0,#STDIN                               // Linux input console
    ldr x1,qAdrsBuffer                          // buffer address 
    mov x2,#BUFFERSIZE                          // buffer size 
    mov x8, #READ                               // request to read datas
    svc 0                                       // call system
    ldr x1,qAdrsBuffer                          // buffer address 
    mov x2,#0                                   // end of string
    sub x0,x0,#1                                   // replace character 0xA
    strb w2,[x1,x0]                             // store byte at the end of input string (x0 contains number of characters)
    ldr x0,qAdrsBuffer
    bl controlNumber                            // call routine
    cmp x0,#0
    bne 1f
    ldr x0,qAdrszMessError                      // not a number
    bl affichageMess
    b 5f
1:
    cmp x0,#1
    bne 2f
    ldr x0,qAdrszMessInteger                    // integer
    bl affichageMess
    b 5f
2:
    cmp x0,#2
    bne 3f
    ldr x0,qAdrszMessFloat                      // float
    bl affichageMess
    b 5f
3:
    cmp x0,#3
    bne 5f
    ldr x0,qAdrszMessFloatExp                   // float with exposant
    bl affichageMess
5:
    b loop

100:                                            // standard end of the program
    mov x0, #0                                  // return code
    mov x8, #EXIT                               // request to exit program
    svc 0                                       // perform system call
qAdrszMessNum:            .quad szMessNum
qAdrszMessError:          .quad szMessError
qAdrszMessInteger:        .quad szMessInteger
qAdrszMessFloat:          .quad szMessFloat
qAdrszMessFloatExp:       .quad szMessFloatExp
qAdrszCarriageReturn:     .quad szCarriageReturn
qAdrsBuffer:              .quad sBuffer
/******************************************************************/
/*     control if string is number                          */ 
/******************************************************************/
/* x0 contains the address of the string */
/* x0 return 0 if not a number       */
/* x0 return 1 if integer   eq 12345 or -12345      */
/* x0 return 2 if float     eq 123.45 or 123,45  or -123,45     */
/* x0 return 3 if float with exposant  eq 123.45E30 or -123,45E-30        */
controlNumber:
    stp x1,lr,[sp,-16]!    // save  registers
    stp x2,x3,[sp,-16]!    // save  registers
    stp x4,x5,[sp,-16]!    // save  registers
    mov x1,#0
    mov x3,#0              // point counter 
1:
    ldrb w2,[x0,x1]
    cmp x2,#0              // end string ?
    beq 7f
    cmp x2,#' '            // space ?
    bne 3f
    add x1,x1,#1
    b   1b                 // loop 
3:
    cmp x2,#'-'            // negative ?
    bne 4f
    add x1,x1,#1
    b 5f
4:
    cmp x2,#'+'            // positive ?
    bne 5f
    add x1,x1,#1
5:
    ldrb w2,[x0,x1]        // control space
    cmp x2,#0              // end ?
    beq 7f
    cmp x2,#' '            // space ?
    bne 6f
    add x1,x1,#1
    b 5b                   // loop
6:
    ldrb w2,[x0,x1]
    cmp x2,#0              // end ?
    beq 14f
    cmp x2,#'E'            // exposant ?
    beq 9f
    cmp x2,#'e'            // exposant ?
    beq 9f
    cmp x2,#'.'            // point ?
    bne 7f
    add x3,x3,#1           // yes increment counter
    add x1,x1,#1
    b 6b                   // and loop
7:
    cmp x2,#','            // comma ?
    bne 8f
    add x3,x3,#1           // yes increment counter
    add x1,x1,#1
    b 6b                   // and loop
8:
    cmp x2,#'0'            // control digit < 0
    blt 99f
    cmp x2,#'9'            // control digit > 0
    bgt 99f
    add x1,x1,#1           // no error loop digit
    b 6b

9:                         // float with exposant
    add x1,x1,#1
    ldrb w2,[x0,x1]
    cmp x2,#0              // end ?
    beq 99f

    cmp x2,#'-'            // negative exposant ?
    bne 10f
    add x1,x1,#1
10:
    mov x4,#0              // nombre de chiffres 
11:
    ldrb w2,[x0,x1]
    cmp x2,#0              // end ?
    beq 13f
    cmp x2,#'0'            // control digit < 0
    blt 99f
    cmp x2,#'9'            // control digit > 9
    bgt 99f
    add x1,x1,#1
    add x4,x4,#1           // counter digit
    b 11b                  // and loop

13:
    cmp x4,#0              // number digit exposant = 0 -> error 
    beq 99f                // error
    cmp x4,#2              // number digit exposant > 2 -> error 
    bgt 99f                // error

    mov x0,#3              // valid float with exposant
    b 100f
14:
    cmp x3,#0
    bne 15f
    mov x0,#1              // valid integer
    b 100f
15:
    cmp x3,#1             // number of point or comma = 1 ?
    blt 100f
    bgt 99f               // error
    mov x0,#2             // valid float
    b 100f
99:
    mov x0,#0             // error
100:
    ldp x4,x5,[sp],16     // restaur  2 registres
    ldp x2,x3,[sp],16     // restaur  2 registres
    ldp x1,lr,[sp],16     // restaur  2 registres
    ret
 
/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"

Action!

Using string <-> number conversion

The solution below uses conversion string to number and number to string to determine if the string is numeric.

Library: Action! Tool Kit

INCLUDE "D2:REAL.ACT" ;from the Action! Tool Kit

BYTE FUNC AreEqual(CHAR ARRAY a,b)
  BYTE i

  IF a(0)#b(0) THEN
    RETURN (0)
  FI
  FOR i=1 to a(0)
  DO
    IF a(i)#b(i) THEN
      RETURN (0)
    FI
  OD
RETURN (1)

BYTE FUNC IsNumeric(CHAR ARRAY s)
  CHAR ARRAY tmp(20)
  INT i
  CARD c
  REAL r

  i=ValI(s)
  StrI(i,tmp)
  IF AreEqual(s,tmp) THEN
    RETURN (1)
  FI

  c=ValC(s)
  StrC(c,tmp)
  IF AreEqual(s,tmp) THEN
    RETURN (1)
  FI
    
  ValR(s,r)
  StrR(r,tmp)
  IF AreEqual(s,tmp) THEN
    RETURN (1)
  FI
RETURN (0)

PROC Test(CHAR ARRAY s)
  BYTE res

  res=IsNumeric(s)
  Print(s)
  Print(" is ")
  IF res=0 THEN
    Print("not ")
  FI
  PrintE("a number.")
RETURN

PROC Main()
  Put(125) PutE() ;clear the screen
  Test("56233")
  Test("-315")
  Test("1.36")
  Test("-5.126")
  Test("3.7E-05")
  Test("1.23BC")
  Test("5.6.3")
RETURN

Using a finite-state machine

The solution below uses a finite-state machine to determine if a string is numeric.

BYTE FUNC IsSign(CHAR c)
  IF c='- OR c='+ THEN
    RETURN (1)
  FI
RETURN (0)

BYTE FUNC IsDigit(CHAR c)
  IF c>='0 AND c<='9 THEN
    RETURN (1)
  FI
RETURN (0)

BYTE FUNC IsDot(CHAR c)
  IF c='. THEN
    RETURN (1)
  FI
RETURN (0)

BYTE FUNC IsExpSymbol(CHAR c)
  IF c='E OR c='e THEN
    RETURN (1)
  FI
RETURN (0)

BYTE FUNC IsNumeric(CHAR ARRAY s)
  DEFINE S_BEGIN="0"
  DEFINE S_SIGN="1"
  DEFINE S_BEFORE_DOT="2"
  DEFINE S_DOT="3"
  DEFINE S_AFTER_DOT="4"
  DEFINE S_EXP_SYMBOL="5"
  DEFINE S_EXP_SIGN="6"
  DEFINE S_EXP="7"
  
  BYTE i,state
  CHAR c

  i=1
  state=S_BEGIN
  WHILE i<=s(0)
  DO
    c=s(i)

    IF state=S_BEGIN THEN
      IF IsSign(c) THEN
        state=S_SIGN
      ELSEIF IsDigit(c) THEN
        state=S_BEFORE_DOT
      ELSEIF IsDot(c) THEN
        state=S_DOT
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_SIGN THEN
      IF IsDigit(c) THEN
        state=S_BEFORE_DOT
      ELSEIF IsDot(c) THEN
        state=S_DOT
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_BEFORE_DOT THEN
      IF IsDigit(c) THEN
        state=S_BEFORE_DOT
      ELSEIF IsDot(c) THEN
        state=S_DOT
      ELSEIF IsExpSymbol(c) THEN
        state=S_EXP_SYMBOL
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_DOT THEN
      IF IsDigit(c) THEN
        state=S_AFTER_DOT
      ELSEIF IsExpSymbol(c) THEN
        state=S_EXP_SYMBOL
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_AFTER_DOT THEN
      IF IsDigit(c) THEN
        state=S_AFTER_DOT
      ELSEIF IsExpSymbol(c) THEN
        state=S_EXP_SYMBOL
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_EXP_SYMBOL THEN
      IF IsSign(c) THEN
        state=S_EXP_SIGN
      ELSEIF IsDigit(c) THEN
        state=S_EXP
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_EXP_SIGN THEN
      IF IsDigit(c) THEN
        state=S_EXP
      ELSE
        RETURN (0)
      FI
    ELSEIF state=S_EXP THEN
      IF IsDigit(c) THEN
        state=S_EXP
      ELSE
        RETURN (0)
      FI
    ELSE
      RETURN (0)
    FI
    i==+1
  OD

  IF state=S_BEGIN OR state=S_DOT OR
    state=S_EXP_SIGN OR state=S_EXP_SIGN THEN
    RETURN (0)
  FI
RETURN (1)

PROC Test(CHAR ARRAY s)
  BYTE res

  res=IsNumeric(s)
  Print(s)
  Print(" is ")
  IF res=0 THEN
    Print("not ")
  FI
  PrintE("a number.")
RETURN

PROC Main()
  Test("56233")
  Test("-315")
  Test("1.36")
  Test("-5.126")
  Test("3.7E-05")
  Test("1.23BC")
  Test("5.6.3")
RETURN

Output:

Screenshot from Atari 8-bit computer

56233 is a number.
-315 is a number.
1.36 is a number.
-5.126 is a number.
3.7E-05 is a number.
1.23BC is not a number.
5.6.3 is not a number.

ActionScript

public function isNumeric(num:String):Boolean
{
    return !isNaN(parseInt(num));
}

Ada

The first file is the package interface containing the declaration of the Is_Numeric function.

package Numeric_Tests is
   function Is_Numeric (Item : in String) return Boolean;
end Numeric_Tests;

The second file is the package body containing the implementation of the Is_Numeric function.

package body Numeric_Tests is
   function Is_Numeric (Item : in String) return Boolean is
      Dummy : Float;
   begin
      Dummy := Float'Value (Item);
      return True;
   exception
      when others =>
         return False;
   end Is_Numeric;
end Numeric_Tests;

The last file shows how the Is_Numeric function can be called.

with Ada.Text_Io; use Ada.Text_Io;
with Numeric_Tests; use Numeric_Tests; 

procedure Is_Numeric_Test is
   S1 : String := "152";
   S2 : String := "-3.1415926";
   S3 : String := "Foo123";
begin
   Put_Line(S1 & " results in " & Boolean'Image(Is_Numeric(S1)));
   Put_Line(S2 & " results in " & Boolean'Image(Is_Numeric(S2)));
   Put_Line(S3 & " results in " & Boolean'Image(Is_Numeric(S3)));
end Is_Numeric_Test;

Output:

 152 results in TRUE
 -3.1415926 results in TRUE
 Foo123 results in FALSE

Aime

integer
is_numeric(text s)
{
    return !trap_q(alpha, s, 0);
}

integer
main(void)
{
    if (!is_numeric("8192&*")) {
        o_text("Not numeric.\n");
    }
    if (is_numeric("8192")) {
        o_text("Numeric.\n");
    }

    return 0;
}

ALGOL 68

Translation of: Ada

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

PROC is numeric = (REF STRING string) BOOL: (
  BOOL out := TRUE;
  PROC call back false = (REF FILE f)BOOL: (out:= FALSE; TRUE);

  FILE memory;
  associate(memory, string);
  on value error(memory, call back false);
  on logical file end(memory, call back false);

  UNION (INT, REAL, COMPL) numeric:=0.0;
  # use a FORMAT pattern instead of a regular expression #
  getf(memory, ($gl$, numeric));
  out
);

test:(
   STRING
     s1 := "152",
     s2 := "-3.1415926",
     s3 := "Foo123";
   print((
     s1, " results in ", is numeric(s1), new line,
     s2, " results in ", is numeric(s2), new line,
     s3, " results in ", is numeric(s3), new line
   ))
)

Output:

152 results in T
-3.1415926 results in T
Foo123 results in F

ALGOL W

begin

    % determnines whether the string contains an integer, real or imaginary  %
    % number. Returns true if it does, false otherwise                       %
    logical procedure isNumeric( string(32) value text ) ;
        begin

            logical ok;
            % the "number" cannot be blank                                   %
            ok := ( text not = " " );
            if ok then begin

                % there is at least one non-blank character                  %
                % must have either an integer or real/immaginary number      %
                % integer: [+|-]digit-sequence                               %
                % real:    [+|-][digit-sequence].digit-sequence['integer][L] %
                % or:      [+|-]digit-sequence[.[digit-sequence]]'integer[L] %
                % imaginary:                                                 %
                %          [+|-][digit-sequence].digit-sequence['integer][L]I%
                % or:      [+|-]digit-sequence[.[digit-sequence]]'integer[L]I%
                % The "I" at the end of an imaginary number can appear       %
                % before or after the "L" (which indicates a long number)    %
                % the "I" and "L" can be in either case                      %

                procedure nextChar ; charPos := charPos + 1;
                logical procedure have( string(1) value ch ) ;
                    ( charPos <= maxChar and text(charPos//1) = ch ) ;

                logical procedure haveDigit ;
                    ( charPos <= maxChar and text(charPos//1) >= "0" and text(charPos//1) <= "9" ) ;


                integer charPos, maxChar;
                logical hadDigits, isReal;
                charPos   :=  0;
                maxChar   := 31;
                hadDigits := false;
                isReal    := false;

                % skip trailing spaces                                       %
                while maxChar > 0 and text(maxChar//1) = " " do maxChar := maxChar - 1;
                % skip leading spacesx                                       %
                while have( " " ) do nextChar;

                % skip optional sign                                         %
                if have( "+" ) or have( "-" ) then nextChar;

                if      haveDigit then begin
                    % have a digit sequence                                  %
                    hadDigits := true;
                    while haveDigit do nextChar
                end if_have_sign ;

                if have( "." ) then begin
                    % real or imaginary number                               %
                    nextChar;
                    isReal    := true;
                    hadDigits := hadDigits or haveDigit;
                    while haveDigit do nextChar
                end if_have_point ;

                % should have had some digits                                %
                ok := hadDigits;

                if ok and have( "'" ) then begin
                    % the number has an exponent                             %
                    isReal := true;
                    nextChar;
                    % skip optional sign                                     %
                    if have( "+" ) or have( "-" ) then nextChar;
                    % must have a digit sequence                             %
                    ok := haveDigit;
                    while haveDigit do nextChar;
                end if_ok_and_have_exponent ;

                % if it is a real number, there could be L/I suffixes        %
                if ok and isReal then begin
                    integer LCount, ICount;
                    LCount := 0;
                    ICount := 0;
                    while have( "L" ) or have( "l" ) or have( "I" ) or have( "i" ) do begin
                        if have( "L" ) or have( "l" )
                        then LCount := LCount + 1
                        else ICount := ICount + 1;
                        nextChar
                    end while_have_L_or_I ;
                    % there can be at most one L and at most 1 I             %
                    ok := ( LCount < 2 and ICount < 2 )
                end if_ok_and_isReal ;

                % must now be at the end if the number                       %
                ok := ok and charPos >= maxChar

            end if_ok ;

            ok
        end isNumeric ;


    % test the isNumeric procedure                                           %
    procedure testIsNumeric( string(32) value n
                           ; logical    value expectedResult
                           ) ;
        begin
            logical actualResult;
            actualResult := isNumeric( n );
            write( s_w := 0
                 , """", n, """ is "
                 , if actualResult then "" else "not "
                 , "numeric "
                 , if actualResult = expectedResult then "" else " NOT "
                 , "as expected"
                 )
        end testIsNumeric ;


    testIsNumeric(          "", false );
    testIsNumeric(         "b", false );
    testIsNumeric(         ".", false );
    testIsNumeric(       ".'3", false );
    testIsNumeric(       "3.'", false );
    testIsNumeric(    "0.0z44", false );
    testIsNumeric(      "-1IL", false );
    testIsNumeric( "4.5'23ILL", false );

    write( "---------" );

    testIsNumeric(        "-1", true  );
    testIsNumeric(    " +.345", true  );
    testIsNumeric(   "4.5'23I", true  );
    testIsNumeric(    "-5'+3i", true  );
    testIsNumeric(    "-5'-3l", true  );
    testIsNumeric(  " -.345LI", true  );

end.

Output:

"                                " is not numeric as expected
"b                               " is not numeric as expected
".                               " is not numeric as expected
".'3                             " is not numeric as expected
"3.'                             " is not numeric as expected
"0.0z44                          " is not numeric as expected
"-1IL                            " is not numeric as expected
"4.5'23ILL                       " is not numeric as expected
---------
"-1                              " is numeric as expected
" +.345                          " is numeric as expected
"4.5'23I                         " is numeric as expected
"-5'+3i                          " is numeric as expected
"-5'-3l                          " is numeric as expected
" -.345LI                        " is numeric as expected

Apex

The isNumeric() method is part of the Apex String Class. Note that it will return false if applied to a decimal, because the '.' character is not a Unicode digit.

String numericString = '123456';
String partlyNumericString = '123DMS';
String decimalString = '123.456';

System.debug(numericString.isNumeric()); // this will be true
System.debug(partlyNumericString.isNumeric()); // this will be false
System.debug(decimalString.isNumeric()); // this will be false
System.debug(decimalString.remove('.').isNumeric()); // this will be true

APL

Works with: Dyalog APL

      ⊃⎕VFI{w←⍵⋄((w='-')/w)←'¯'⋄w}'152 -3.1415926 Foo123'

1 1 0

Works with more recent versions of Dyalog APL

       ⊃⎕VFI '¯' @ ('-'∘=)   '152 -3.1415926 Foo123'     ⍝ Fast:  replacement of - with APL high-minus required for ⎕VFI 
1 1 0
       ⊃⎕VFI '-' ⎕R '¯'    ⊣ '152 -3.1415926 Foo123'     ⍝ Simple: (ditto)
1 1 0

Works with: GNU APL

      {∧/⍵∊(⊃,¨'0123456789¯.+')}¨'152' '¯3.1415926' 'Foo123'
1 1 0

AppleScript

-- isNumString :: String -> Bool
on isNumString(s)
    try
        if class of s is string then
            set c to class of (s as number)
            c is real or c is integer
        else
            false
        end if
    on error
        false
    end try
end isNumString



-- TEST
on run
    
    map(isNumString, {3, 3.0, 3.5, "3.5", "3E8", "-3.5", "30", "three", three, four})
    
    --> {false, false, false, true, true, true, true, false, false, false}
    
end run

-- three :: () -> Int
script three
    3
end script

-- four :: () -> Int
on four()
    4
end four


-- GENERIC FUNCTIONS FOR TEST

-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    tell mReturn(f)
        set lng to length of xs
        set lst to {}
        repeat with i from 1 to lng
            set end of lst to lambda(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map


-- Lift 2nd class handler function into 1st class script wrapper 
-- mReturn :: Handler -> Script
on mReturn(f)
    if class of f is script then
        f
    else
        script
            property lambda : f
        end script
    end if
end mReturn

Output:

{false, false, false, true, true, true, true, false, false, false}

The classic way's slightly simpler, since the coercion result must be a real or an integer if the coercion itself didn't error.

on isNumString(s)
    if (s's class is not text) then return false
    try
        s as number
        return true
    on error
        return false
    end try
end isNumString

ARM Assembly

Works with: as version Raspberry Pi

/* ARM assembly Raspberry PI  */
/*  program strNumber.s   */

/* Constantes    */
.equ STDIN,  0                           @ Linux input console
.equ STDOUT, 1                           @ Linux output console
.equ EXIT,   1                           @ Linux syscall
.equ READ,   3                           @ Linux syscall
.equ WRITE,  4                           @ Linux syscall

.equ BUFFERSIZE,          100


/* Initialized data */
.data
szMessNum: .asciz "Enter number : \n"

szMessError:            .asciz "String is not a number !!!\n"
szMessInteger:          .asciz "String is a integer.\n"
szMessFloat:            .asciz "String is a float.\n"
szMessFloatExp:         .asciz "String is a float with exposant.\n"
szCarriageReturn:       .asciz "\n"

/* UnInitialized data */
.bss 
sBuffer:              .skip BUFFERSIZE

/*  code section */
.text
.global main 
main: 

loop:
    ldr r0,iAdrszMessNum
    bl affichageMess
    mov r0,#STDIN                               @ Linux input console
    ldr r1,iAdrsBuffer                          @ buffer address 
    mov r2,#BUFFERSIZE                          @ buffer size 
    mov r7, #READ                               @ request to read datas
    swi 0                                       @ call system
    ldr r1,iAdrsBuffer                          @ buffer address 
    mov r2,#0                                   @ end of string
    sub r0,#1                                   @ replace character 0xA
    strb r2,[r1,r0]                             @ store byte at the end of input string (r0 contains number of characters)
    ldr r0,iAdrsBuffer
    bl controlNumber                            @ call routine
    cmp r0,#0
    bne 1f
    ldr r0,iAdrszMessError                      @ not a number
    bl affichageMess
    b 5f
1:
    cmp r0,#1
    bne 2f
    ldr r0,iAdrszMessInteger                    @ integer
    bl affichageMess
    b 5f
2:
    cmp r0,#2
    bne 3f
    ldr r0,iAdrszMessFloat                      @ float
    bl affichageMess
    b 5f
3:
    cmp r0,#3
    bne 5f
    ldr r0,iAdrszMessFloatExp                   @ float with exposant
    bl affichageMess
5:
    b loop

100:                                            @ standard end of the program
    mov r0, #0                                  @ return code
    mov r7, #EXIT                               @ request to exit program
    svc 0                                       @ perform system call
iAdrszMessNum:            .int szMessNum
iAdrszMessError:          .int szMessError
iAdrszMessInteger:        .int szMessInteger
iAdrszMessFloat:          .int szMessFloat
iAdrszMessFloatExp:       .int szMessFloatExp
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrsBuffer:              .int sBuffer
/******************************************************************/
/*     control if string is number                          */ 
/******************************************************************/
/* r0 contains the address of the string */
/* r0 return 0 if not a number       */
/* r0 return 1 if integer   eq 12345 or -12345      */
/* r0 return 2 if float     eq 123.45 or 123,45  or -123,45     */
/* r0 return 3 if float with exposant  eq 123.45E30 or -123,45E-30        */
controlNumber:
    push {r1-r4,lr}                       @ save  registers 
    mov r1,#0
    mov r3,#0          @ point counter 
1:
    ldrb r2,[r0,r1]
    cmp r2,#0
    beq 5f
    cmp r2,#' '
    addeq r1,#1
    beq   1b
    cmp r2,#'-'                    @ negative ?
    addeq r1,#1
    beq 2f
    cmp r2,#'+'                    @ positive ?
    addeq r1,#1
2:
    ldrb r2,[r0,r1]                @ control space
    cmp r2,#0                      @ end ?
    beq 5f
    cmp r2,#' '
    addeq r1,#1
    beq 2b
3:
    ldrb r2,[r0,r1]
    cmp r2,#0                 @ end ?
    beq 10f
    cmp r2,#'E'               @ exposant ?
    beq 6f
    cmp r2,#'e'               @ exposant ?
    beq 6f
    cmp r2,#'.'               @ point ?
    addeq r3,#1               @ yes increment counter
    addeq r1,#1
    beq 3b
    cmp r2,#','               @ comma ?
    addeq r3,#1               @ yes increment counter
    addeq r1,#1
    beq 3b
    cmp r2,#'0'               @ control digit < 0
    blt 5f
    cmp r2,#'9'               @ control digit > 0
    bgt 5f
    add r1,#1                 @ no error loop digit
    b 3b
5:                            @ error detected
    mov r0,#0
    b 100f
6:    @ float with exposant
    add r1,#1
    ldrb r2,[r0,r1]
    cmp r2,#0             @ end ?
    moveq r0,#0           @ error
    beq 100f
    cmp r2,#'-'           @ negative exposant ?
    addeq r1,#1
    mov r4,#0             @ nombre de chiffres 
7:
    ldrb r2,[r0,r1]
    cmp r2,#0             @ end ?
    beq 9f
    cmp r2,#'0'           @ control digit < 0
    blt 8f
    cmp r2,#'9'           @ control digit > 0
    bgt 8f
    add r1,#1
    add r4,#1             @ counter digit
    b 7b
8:
    mov r0,#0
    b 100f
9:
    cmp r4,#0             @ number digit exposant = 0 -> error 
    moveq r0,#0           @ erreur
    beq 100f
    cmp r4,#2             @ number digit exposant > 2 -> error 
    movgt r0,#0           @ error
    bgt 100f
    mov r0,#3             @ valid float with exposant
    b 100f
10:
    cmp r3,#0
    moveq r0,#1           @ valid integer
    beq 100f
    cmp r3,#1             @ number of point or comma = 1 ?
    moveq r0,#2           @ valid float
    movgt r0,#0           @ error
100:
    pop {r1-r4,lr}                         @ restaur des  2 registres
    bx lr                                        @ return
/******************************************************************/
/*     display text with size calculation                         */ 
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                       @ save  registers 
    mov r2,#0                                   @ counter length */
1:                                              @ loop length calculation
    ldrb r1,[r0,r2]                             @ read octet start position + index 
    cmp r1,#0                                   @ if 0 its over
    addne r2,r2,#1                              @ else add 1 in the length
    bne 1b                                      @ and loop 
                                                @ so here r2 contains the length of the message 
    mov r1,r0                                   @ address message in r1 
    mov r0,#STDOUT                              @ code to write to the standard output Linux
    mov r7, #WRITE                              @ code call system "write" 
    svc #0                                      @ call system
    pop {r0,r1,r2,r7,lr}                        @ restaur registers
    bx lr                                       @ return

Arturo

print numeric? "hello world"
print numeric? "1234"
print numeric? "1234 hello world"
print numeric? "12.34"
print numeric? "!#@$"
print numeric? "-1.23"

Output:

false
true
false
true
false
true

AutoHotkey

AutoHotkey has no explicitly defined variable types. A variable containing only digits (with an optional decimal point) is automatically interpreted as a number when a math operation or comparison requires it.

list = 0 .14 -5.2 ten 0xf
Loop, Parse, list, %A_Space%
  MsgBox,% IsNumeric(A_LoopField)
Return

IsNumeric(x) {
  If x is number
    Return, 1
  Else Return, 0
}

;Output: 1  1  1  0  1

AWK

The following function uses the fact that non-numeric strings in AWK are treated as having the value 0 when used in arithmetics, but not in comparison:

$ awk 'function isnum(x){return(x==x+0)} BEGIN{print isnum("hello"),isnum("-42")}'

Output:

0 1

BaCon

INPUT "Your string: ", s$

IF REGEX(s$, "^[-+]?[0-9]*\\.?[0-9]+([eE][-+]?[0-9]+)?$") THEN
    PRINT "This is a number"
ELSE
    PRINT "Not a number"
ENDIF

Output:

user@host $ ./isnumber 
Your string: 12.3
This is a number
user@host $ ./isnumber 
Your string: 12E3
This is a number
user@host $ ./isnumber 
Your string: PI
Not a number
user@host $ ./isnumber 
Your string: Hello
Not a number

BASIC

10 INPUT "Enter a string";S$:GOSUB 1000
20 IF R THEN PRINT "Is num" ELSE PRINT"Not num"
99 END
1000 T1=VAL(S$):T1$=STR$(T1)
1010 R=T1$=S$ OR T1$=" "+S$
1099 RETURN

BASIC256

#La función isNumeric() es nativa de BASIC256.
#Devuelve 1 (verdadero) si la expresión es un entero, 
#un número de punto flotante o una cadena que se puede
#convertir directamente en un número. 
#De lo contrario, devuelve 0 (falso).

#Las siguientes cadenas numéricas son válidas: 
#“123”, “-345”, “234.234324”, “-34234.123”, “-2.567e7” y “6.7888E-8”. 

s = "1234.056789"
print s, " => "; isNumeric(s)
s = "-2.567e7"
print s, " => "; isNumeric(s)
s = "Dog"
print s, " => "; isNumeric(s)
s = "Bad125"
print s, " => "; isNumeric(s)
s = "-0177"
print s, " => "; isNumeric(s)
s = "0b1110" #binario
print s, " => "; isNumeric(s)
s = "0o177" #octal
print s, " => "; isNumeric(s)
s = "0xff"  #hexadecimal
print s, " => "; isNumeric(s)
end

Output:

1234.056789    => 1
-2.567e7       => 1
Dog            => 0
Bad125         => 0
-0177          => 1
0b1110         => 1
0o177          => 1
0xff           => 0

Commodore BASIC

5 print chr$(147);chr$(14)
10 input "Enter a string";s$:gosub 1000:print
20 if r then print "You entered a number.":goto 99
30 print "That is not a number."
99 end
1000 t1=val(s$):t1$=str$(t1)
1010 r=t1$=s$ or t1$=" "+s$
1099 return

Output:

Enter a string? 15893

You entered a number.

ready.
run

Enter a string? Llamas

That is not a number.

ready.
█

QB64

Input "Enter a text or a number: ", v$ 'The "$" establishes that this is a string variable. So whatever entered will be stored as 
                                       'a string.
If v$ = Str$(Val(v$)) Then             'Str$() converts numeric values to their string counter parts and Val() does the opposite,
                                       'converting strings to their numerical values. By converting the value of whatever is stored
                                       'in v$ to a number and then back to a string it will have either stayed completely the same, 
                                       'in which case it is a numeric value (including exponent and hex and oct based numbers) or
                                       'what is returned by the nested Str$() and Val$() functions will be different, in which case
                                       'one, the other, or both returned an error or a truncation of the original string which began
                                       'with numeric characters but was not entirely a number, such as "99, rue de Rivoli".
     Print "Your entered a number."
Else
     Print "You did not enter a number."
End If
Sleep
System

Output:

Enter a text or a number: 12345
You entered a number.

Enter a text or a number: Four
You did not enter a number.

Enter a text or a number: 99, rue de Rivoli
You did not enter a number.

Enter a text or a number: 9E4
You entered a number.

NB: While "99, rue de Rivoli" contains a number it is not a number entirely. The Val(v$) in this case would have stopped after it converted the "99" portion of the input, which when converted back to a string and compared to the original input would not result in an equality. 9E4 the program reads as an exponential value.

Batch File

set /a a=%arg%+0 >nul
if %a% == 0 (
	if not "%arg%"=="0" (
		echo Non Numeric.
	) else (
		echo Numeric.
	)
) else (
	echo Numeric.
)

BBC BASIC

Works with: BBC BASIC for Windows

      REPEAT
        READ N$
        IF FN_isanumber(N$) THEN
          PRINT "'" N$ "' is a number"
        ELSE
          PRINT "'" N$ "' is NOT a number"
        ENDIF
      UNTIL N$ = "end"
      END
      
      DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0"
      DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"
      
      DEF FN_isanumber(A$)
      ON ERROR LOCAL = FALSE
      IF EVAL("(" + A$ + ")") <> VAL(A$) THEN = FALSE
      IF VAL(A$) <> 0 THEN = TRUE
      IF LEFT$(A$,1) = "0" THEN = TRUE
      = FALSE

Output:

'PI' is NOT a number
'0123' is a number
'-0123' is a number
'12.30' is a number
'-12.30' is a number
'123!' is NOT a number
'0' is a number
'0.0' is a number
'.123' is a number
'-.123' is a number
'12E3' is a number
'12E-3' is a number
'12+3' is NOT a number
'end' is NOT a number

Befunge

 ~:0\`#v_:"+"-!#v_:"-"-!#v_::"E"-\"e"-*#v_                               v
v       _v#     <        <             0<
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!#v_                 v
^                           $<        >                 > $               v
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!#v_>                v>
^                           $<                        >$~:0\`#v_:"+"-#v_v
v      $_v#                                                     < <   :#<
>~:0\`#v_>::"0"-0\`\"9"-0`+!#v_:"."-!#v_::"E"-\"e"-*!v          0     > v
^                           $<        v                 <    << ^_^#-"-"<
       > "ciremuN">:#,_@             >>#$_"ciremun toN">:#,_@^           <

Although only integer inputs are strictly allowed in Befunge, the code tries to adhere to the floating point conventions in other languages when recognising valid numbers.

Output:

'PI' Not numeric
'0123' Numeric
'-0123' Numeric
'12.30' Numeric
'-12.30' Numeric
'123!' Not numeric
'0' Numeric
'0.0' Numeric
'.123' Numeric
'-.123' Numeric
'12E3' Numeric
'12E-3' Numeric
'12+3' Not numeric
'end' Not numeric
'12..34' Not numeric
'12e3.4' Not numeric
'192.168.0.1' Not numeric

BQN

IsNumeric ← 1∘•ParseFloat⎊0

Bracmat

To check whether a string is a number, a fraction or an integer, use the patterns #, / and ~/# ("not a fraction and yet a number"). In the pattern matching examples below (which can be typed in at the Bracmat prompt) F denotes 'failure' and S denotes 'success'.

43257349578692:/
    F

260780243875083/35587980:/
    S
    
247/30:~/#
    F

80000000000:~/#
    S

The pattern ~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#) recognises string representations of floating point numbers.

@("1.000-4E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 F

@("1.0004E-54328":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("-464641.0004E-54328":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("1/2.0004E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 F

@("1357E-10":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("1357e0":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("13579":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("1.246":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("0.0":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

@("0.0000":~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#))
 S

Calculations with floating point numbers are delegated to UFP (Un-I-fancy-fied Floating Point, because it took me 30 years to dream up a viable way to do FP in Bracmat without breaking existing code) objects. An UFP object compiles and executes code that only handles C "doubles" and (multidimensional) arrays of such values.

Burlesque

ps^^-]to{"Int""Double"}\/~[\/L[1==?*

Assumes string is not empty.

C

Returns true (non-zero) if character-string parameter represents a signed or unsigned floating-point number. Otherwise returns false (zero).

#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>

bool isNumeric(const char *s) {
    if (s == NULL || *s == '\0' || isspace(*s)) {
        return false;
    }
    char *p;
    strtod(s, &p);
    return *p == '\0';
}

C#

Framework: .NET 2.0+

public static bool IsNumeric(string s)
{
    double Result;
    return double.TryParse(s, out Result);  // TryParse routines were added in Framework version 2.0.
}        

string value = "123";
if (IsNumeric(value)) 
{
  // do something
}

Framework: .NET 1.0+

public static bool IsNumeric(string s)
{
  try
  {
    Double.Parse(s);
    return true;
  }
  catch
  {
    return false;
  }
}

C++

Translation of: C

#include <cctype>
#include <cstdlib>

bool isNumeric(const char *s) {
    if (s == nullptr || *s == '\0' || std::isspace(*s)) {
        return false;
    }
    char *p;
    std::strtod(s, &p);
    return *p == '\0';
}

Using stringstream:

#include <sstream> // for istringstream

using namespace std;

bool isNumeric( const char* pszInput, int nNumberBase )
{
	istringstream iss( pszInput );

	if ( nNumberBase == 10 )
	{
		double dTestSink;
		iss >> dTestSink;
	}
	else if ( nNumberBase == 8 || nNumberBase == 16 )
	{
		int nTestSink;
		iss >> ( ( nNumberBase == 8 ) ? oct : hex ) >> nTestSink;
	}
	else
		return false;

	// was any input successfully consumed/converted?
	if ( ! iss )
		return false;

	// was all the input successfully consumed/converted?
	return ( iss.rdbuf()->in_avail() == 0 );
}

Using find:

bool isNumeric( const char* pszInput, int nNumberBase )
{
	string base = "0123456789ABCDEF";
	string input = pszInput;

	return (input.find_first_not_of(base.substr(0, nNumberBase)) == string::npos);
}

Using all_of (requires C++11)

bool isNumeric(const std::string& input) {
    return std::all_of(input.begin(), input.end(), ::isdigit);
}

CFScript

ColdFusion Script (CfScript)

isNumeric(42)

Clojure

(defn numeric? [s]
  (if-let [s (seq s)]
    (let [s (if (= (first s) \-) (next s) s)
          s (drop-while #(Character/isDigit %) s)
          s (if (= (first s) \.) (next s) s)
          s (drop-while #(Character/isDigit %) s)]
      (empty? s))))

This works with any sequence of characters, not just Strings, e.g.:

(numeric? [\1 \2 \3])  ;; yields logical true

Clojure has a fairly rich set of numeric literals, including Ratios, BigInts and BigDecimals. The Clojure reader will attempt to read any form starting with a digit (optionally preceded by a '+' or '-') as a number. So the following checks to see if such a read is successful:

(require '[clojure.edn :as edn])
(import [java.io PushbackReader StringReader])

(defn number-string? [s]
  (boolean
    (when (and (string? s) (re-matches #"^[+-]?\d.*" s))
      (let [reader (PushbackReader. (StringReader. s))
            num (try (edn/read reader) (catch Exception _ nil))]
        (when num
          ; Check that the string has nothing after the number
          (= -1 (.read reader)))))))

user=> (number-string? "2r101010")
true
user=> (number-string? "22/7")
true

COBOL

Intrinsic Functions

COBOL has the intrinsic functions TEST-NUMVAL and TEST-NUMVAL-C to check if a string is numeric (TEST-NUMVAL-C is used to check if it is also a monetary string). Implementations supporting the 20XX draft standard can also use TEST-NUMVAL-F for floating-point numbers. They return 0 if the string is valid, or the position of the first incorrect character.

        program-id. is-numeric.
        procedure division.
        display function test-numval-f("abc") end-display
        display function test-numval-f("-123.01E+3") end-display
        if function test-numval-f("+123.123") equal zero then
            display "is numeric" end-display
        else
            display "failed numval-f test" end-display
        end-if
        goback.

Implementation

Works with: OpenCOBOL

       IDENTIFICATION DIVISION.
       PROGRAM-ID. Is-Numeric.

       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  Numeric-Chars      PIC X(10) VALUE "0123456789".
       
       01  Success            CONSTANT 0.
       01  Failure            CONSTANT 128.

       LOCAL-STORAGE SECTION.
       01  I                  PIC 99.

       01  Num-Decimal-Points PIC 99.
       01  Num-Valid-Chars    PIC 99.

       LINKAGE SECTION.
       01  Str                PIC X(30). 

       PROCEDURE DIVISION USING Str.
           IF Str = SPACES
               MOVE Failure TO Return-Code
               GOBACK
           END-IF

           MOVE FUNCTION TRIM(Str) TO Str

           INSPECT Str TALLYING Num-Decimal-Points FOR ALL "."
           IF Num-Decimal-Points > 1
               MOVE Failure TO Return-Code
               GOBACK
           ELSE
               ADD Num-Decimal-Points TO Num-Valid-Chars
           END-IF

           IF Str (1:1) = "-" OR "+"
               ADD 1 TO Num-Valid-Chars
           END-IF
           
           PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
               INSPECT Str TALLYING Num-Valid-Chars
                   FOR ALL Numeric-Chars (I:1) BEFORE SPACE
           END-PERFORM

           INSPECT Str TALLYING Num-Valid-Chars FOR TRAILING SPACES

           IF Num-Valid-Chars = FUNCTION LENGTH(Str) 
               MOVE Success TO Return-Code
           ELSE
               MOVE Failure TO Return-Code
           END-IF

           GOBACK
           .

CoffeeScript

The isFinite function is built into JavaScript, so we don't need to create our own function in CoffeeScript.

console.log (isFinite(s) for s in [5, "5", "-5", "5", "5e5", 0]) # all true
console.log (isFinite(s) for s in [NaN, "fred", "###"]) # all false

ColdFusion

Adobe's ColdFusion

<cfset TestValue=34>
  TestValue: <cfoutput>#TestValue#</cfoutput><br>
<cfif isNumeric(TestValue)>
  is Numeric.
<cfelse>
  is NOT Numeric.
</cfif>

<cfset TestValue="NAS">
  TestValue: <cfoutput>#TestValue#</cfoutput><br>
<cfif isNumeric(TestValue)>
  is Numeric.
<cfelse>
  is NOT Numeric.
</cfif>

Alternative solution

<cfoutput>#isNumeric(42)#</cfoutput>

Common Lisp

If the input may be relied upon to not be especially malicious, then it may be read and the result checked for being a number.

(defun numeric-string-p (string)
  (let ((*read-eval* nil))
    (ignore-errors (numberp (read-from-string string)))))

ignore-errors here handles returning nil in case the input is invalid rather than simply non-numeric.

However, read[-from-string] has the side effect of interning any symbols encountered, and can have memory allocation larger than the input size (due to read syntax such as #*, which takes a length). The parse-number library provides a numbers-only equivalent of read.

(defun numeric-string-p (string)
      (ignore-errors (parse-number:parse-number string)))  ; parse failed, return false (nil)

D

Standard Version

Using the standard Phobos function (currently binary and hex literals are not recognized):

import std.stdio, std.string, std.array;

void main() {
    foreach (const s; ["12", " 12\t", "hello12", "-12", "02",
                 "0-12", "+12", "1.5", "1,000", "1_000",
                 "0x10", "0b10101111_11110000_11110000_00110011",
                 "-0b10101", "0x10.5"])
        writefln(`isNumeric("%s"): %s`, s, s.strip().isNumeric(true));
}

Output:

isNumeric("12"): true
isNumeric(" 12  "): true
isNumeric("hello12"): false
isNumeric("-12"): true
isNumeric("02"): true
isNumeric("0-12"): false
isNumeric("+12"): true
isNumeric("1.5"): true
isNumeric("1,000"): true
isNumeric("1_000"): true
isNumeric("0x10"): false
isNumeric("0b10101111_11110000_11110000_00110011"): false
isNumeric("-0b10101"): false
isNumeric("0x10.5"): false

An Implementation

import std.stdio, std.string, std.conv, std.array, std.exception;

bool isNumeric(in string s) pure {
    immutable s2 = s.strip.toLower.replace("_", "").replace(",", "");
    try {
        s2.to!real;
    } catch (ConvException e) {
        if (s2.startsWith("0x"))
            return !s2[2 .. $].to!ulong(16)
                    .collectException!ConvException;
        else if (s2.startsWith("0b"))
            return !s2[2 .. $].to!ulong(2)
                    .collectException!ConvException;
        else
            return false;
    }

    return true;
}

void main() {
    foreach (immutable s; ["12", " 12\t", "hello12", "-12", "02",
                 "0-12", "+12", "1.5", "1,000", "1_000",
                 "0x10", "0b10101111_11110000_11110000_00110011",
                 "-0b10101", "0x10.5"])
        writefln(`isNumeric("%s"): %s`, s, s.isNumeric);
}

Output:

isNumeric("12"): true
isNumeric(" 12  "): true
isNumeric("hello12"): false
isNumeric("-12"): true
isNumeric("02"): true
isNumeric("0-12"): false
isNumeric("+12"): true
isNumeric("1.5"): true
isNumeric("1,000"): true
isNumeric("1_000"): true
isNumeric("0x10"): true
isNumeric("0b10101111_11110000_11110000_00110011"): true
isNumeric("-0b10101"): false
isNumeric("0x10.5"): false

Delphi

This simple function is a wrapper around a built-in Delphi function

function IsNumericString(const inStr: string): Boolean;
var
  i: extended;
begin
  Result := TryStrToFloat(inStr,i);
end;

This console application tests the function:

program isNumeric;

{$APPTYPE CONSOLE}

uses
  Classes,
  SysUtils;

function IsNumericString(const inStr: string): Boolean;
var
  i: extended;
begin
  Result := TryStrToFloat(inStr,i);
end;


{ Test function }
var
  s: string;
  c: Integer;

const
  MAX_TRIES = 10;
  sPROMPT   = 'Enter a string (or type "quit" to exit):';
  sIS       = ' is numeric';
  sISNOT    = ' is NOT numeric';

begin
  c := 0;
  s := '';
  repeat
    Inc(c);
    Writeln(sPROMPT);
    Readln(s);
    if (s <> '') then
      begin
        tmp.Add(s);
        if IsNumericString(s) then
          begin
            Writeln(s+sIS);
          end
          else
          begin
            Writeln(s+sISNOT);
          end;
        Writeln('');
      end;
  until
    (c >= MAX_TRIES) or (LowerCase(s) = 'quit');

end.

Output:

Example summarised

123 is numeric
-123.456 is numeric
-123.-456 is NOT numeric
.345 is numeric
m1k3 is NOT numeric

Dyalect

func String.IsNumeric() {
    try {
        parse(this) is Integer or Float
    } catch _ {
        false
    }
}
 
var str = "1234567"
print(str.IsNumeric())

Déjà Vu

is-numeric s:
	true
	try:
		drop to-num s
	catch value-error:
		not

for v in [ "1" "0" "3.14" "hello" "12e3" "12ef" "-3" ]:
	!.( v is-numeric v )

Output:

"-3" true 
"12ef" false 
"12e3" true 
"hello" false 
"3.14" true 
"0" true 
"1" true

E

def isNumeric(specimen :String) {
    try {
        <import:java.lang.makeDouble>.valueOf(specimen)
        return true
    } catch _ {
       return false
    }
}

EasyLang

func is_numeric a$ .
   h = number a$
   # because every variable must be used
   h = h
   return 1 - error
.
for s$ in [ "abc" "21a" "1234" "-13" "7.65" ]
   if is_numeric s$ = 1
      print s$ & " is numeric"
   else
      print s$ & " is not numeric"
   .
.

EchoLisp

The conversion function string->number returns #f - false - in the string is not a number, else returns a number, which is #t - true - as far as logical operations are concerned

(string->number "albert")
   → #f
(string->number -666)
    → -666
(if (string->number 666) 'YES 'NO)
    → YES

Elixir

defmodule RC do
  def is_numeric(str) do
    case Float.parse(str) do
      {_num, ""} -> true
      _          -> false
    end
  end
end

["123", "-12.3", "123.", ".05", "-12e5", "+123", " 123", "abc", "123a", "12.3e", "1 2"] |> Enum.filter(&RC.is_numeric/1)

Output:

["123", "-12.3", "-12e5", "+123"]

EMal

fun isNumeric = logic by text value
  try
    ^|So funny: 
     |a) we check if it's castable to a real
     |b) we obtain the real 0.0 
     |c) conversion from real to int to get 0
     |d) int can be converted to logical to get ⊥
     |e) we can negate the result
     |^
    return not when(value.contains("."), logic!int!(real!value * 0), logic!(int!value * 0))
  remedy
    return false
  end
end
fun main = int by List args
  if args.length == 1
    writeLine(isNumeric(args[0]))
  else
    writeLine("value".padEnd(8, " ") + " " + "numeric")
    for each text value in text["0o755", "thursday", "3.14", "0b1010", "-100", "0xff"]
      writeLine(value.padEnd(8, " ") + " " + isNumeric(value))
    end
  end
  return 0
end
exit main(Runtime.args)

Output:

value    numeric
0o755    ⊤
thursday ⊥
3.14     ⊤
0b1010   ⊤
-100     ⊤
0xff     ⊤

Erlang

Erlang doesn't come with a way to say if a string represents a numeric value or not, but does come with the built-in function is_number/1, which will return true if the argument passed is either an integer or a float. Erlang also has two functions to transform a string to either a floating number or an integer, which will be used in conjunction with is_number/1.

is_numeric(L) ->
    Float = (catch erlang:list_to_float(L)),
    Int = (catch erlang:list_to_integer(L)),
    is_number(Float) orelse is_number(Int).

ERRE

Short form using predeclared ERRE functions VAL and STR$.

PROGRAM NUMERIC

PROCEDURE IS_NUMERIC(S$->ANS%)
LOCAL T1,T1$
    T1=VAL(S$)
    T1$=STR$(T1)
    ANS%=(T1$=S$) OR T1$=" "+S$
END PROCEDURE

BEGIN
    PRINT(CHR$(12);)
    INPUT("Enter a string",S$)
    IS_NUMERIC(S$->ANS%)
    IF ANS% THEN PRINT("is num") ELSE PRINT("not num")
END PROGRAM

Output:

Enter a string? 12.30
is num

Euphoria

include get.e

function is_numeric(sequence s)
    sequence val
    val = value(s)
    return val[1]=GET_SUCCESS and atom(val[2])
end function

F#

let is_numeric a = fst (System.Double.TryParse a)

Factor

: numeric? ( string -- ? ) string>number >boolean ;

Fantom

The 'fromStr' methods return a parsed number or given an error. The 'false' tells each method to return null if the string does not parse as a number of given type, otherwise, the 'fromStr' method throws an exception.

class Main
{
  // function to see if str contains a number of any of built-in types
  static Bool readNum (Str str)
  {
    int := Int.fromStr (str, 10, false)  // use base 10
    if (int != null) return true
    float := Float.fromStr (str, false)
    if (float != null) return true
    decimal := Decimal.fromStr (str, false)
    if (decimal != null) return true

    return false
  }

  public static Void main ()
  {
    echo ("For '2': " + readNum ("2"))
    echo ("For '-2': " + readNum ("-2"))
    echo ("For '2.5': " + readNum ("2.5"))
    echo ("For '2a5': " + readNum ("2a5"))
    echo ("For '-2.1e5': " + readNum ("-2.1e5"))
  }
}

Output:

For '2': true
For '-2': true
For '2.5': true
For '2a5': false
For '-2.1e5': true

Another example inspired by the Kotlin example. Fantom does not have an enhanced for-loop (foreach) loop, but instead uses Closures as the primary mechanism of iteration.

/* gary chike                                08/27/2023 */

class Main {
    static Void main() {
        inputs := ["152\n", "-3.141", "Foo123", "-0", "456bar", "1.0E10"]

        inputs.each |Str input| { echo("$input.trim \tis " + (isNumeric(input) ? "numeric" : "not numeric"))}

    static Bool isNumeric(Str input) {
        try {
            input.toFloat
            return true
        }
        catch(Err e) {
            return false
        }
    }
}

Output:

152     is numeric
-3.141  is numeric
Foo123  is not numeric
-0      is numeric
456bar  is not numeric
1.0E10  is numeric

Forth

Works with: gforth version 0.6.2

: is-numeric ( addr len -- )
  2dup snumber? ?dup if      \ not standard, but >number is more cumbersome to use
   0< if
     -rot type ."  as integer = " .
   else
     2swap type ."  as double = " <# #s #> type
   then
  else 2dup >float if
    type ."  as float = " f.
  else
    type ."  isn't numeric in base " base @ dec.
  then then ;

s" 1234" is-numeric    \ 1234 as integer = 1234
s" 1234." is-numeric    \ 1234. as double = 1234
s" 1234e" is-numeric    \ 1234e as float = 1234.
s" $1234" is-numeric    \ $1234 as integer = 4660  ( hex literal )
s" %1010" is-numeric    \ %1010 as integer = 10  ( binary literal )
s" beef" is-numeric    \ beef isn't numeric in base 10
hex
s" beef" is-numeric    \ beef as integer = BEEF
s" &1234" is-numeric    \ &1234 as integer = 4D2 ( decimal literal )

Fortran

FUNCTION is_numeric(string)
  IMPLICIT NONE
  CHARACTER(len=*), INTENT(IN) :: string
  LOGICAL :: is_numeric
  REAL :: x
  INTEGER :: e
  READ(string,*,IOSTAT=e) x
  is_numeric = e == 0
END FUNCTION is_numeric

Free Pascal

function isNumeric(const potentialNumeric: string): boolean;
var
	potentialInteger: integer;
	potentialReal: real;
	integerError: integer;
	realError: integer;
begin
	integerError := 0;
	realError := 0;
	
	// system.val attempts to convert numerical value representations.
	// It accepts all notations as they are accepted by the language,
	// as well as the '0x' (or '0X') prefix for hexadecimal values.
	val(potentialNumeric, potentialInteger, integerError);
	val(potentialNumeric, potentialReal, realError);
	
	isNumeric := (integerError = 0) or (realError = 0);
end;

The following is a more complete and compilable example.

program IsNumeric;

type
    TDynamicArrayItem = record
    StrValue: string;
  end;

var
  myDynamicArray: array of TDynamicArrayItem; 
  i: Integer;
  Value: Extended;
  Code: Integer;

begin
  // Initialize the dynamic array with different data types
  SetLength(myDynamicArray, 7);
  myDynamicArray[0].StrValue := 'Hello';
  myDynamicArray[1].StrValue := '42';
  myDynamicArray[2].StrValue := '3.14159';
  myDynamicArray[3].StrValue := 'World';
  myDynamicArray[4].StrValue := '99';
  myDynamicArray[5].StrValue := '0777'; // Octal representation for 511
  myDynamicArray[6].StrValue := '$A1';  // Hexadecimal representation for 161

  // Iterate through the dynamic array and determine data type
  for i := Low(myDynamicArray) to High(myDynamicArray) do
  begin
    Val(myDynamicArray[i].StrValue, Value, Code);
    if Code = 0 then // The value 0 for Code indicates that the conversion was successful.
        Writeln('Element ', i, ': Numeric Value ', Chr(9),' - ', Value) // Chr(9) = tab
    else
        Writeln('Element ', i, ': Non-Numeric Value ', Chr(9), ' - ', myDynamicArray[i].StrValue);
  end;
end.
{ Val converts the value represented in the string 'StrValue' to a numerical value or an enumerated value, and stores this value in the variable 'Value', which can be of type Longint, Real and Byte or any enumerated type. If the conversion isn't successful, then the parameter 'Code' contains the index of the character in 'StrValue' which prevented the conversion. }

Output:

Free Pascal Compiler version 3.2.2 [2021/10/28] for x86_64
Copyright (c) 1993-2021 by Florian Klaempfl and others
Target OS: Darwin for x86_64
Compiling arrVariantIsNumeric.pas
Assembling arrvariantisnumeric
Linking arrVariantIsNumeric
37 lines compiled, 0.3 sec

Element 0: Non-Numeric Value     - Hello
Element 1: Numeric Value         -  4.20000000000000000000E+0001
Element 2: Numeric Value         -  3.14158999999999999993E+0000
Element 3: Non-Numeric Value     - World
Element 4: Numeric Value         -  9.90000000000000000000E+0001
Element 5: Numeric Value         -  7.77000000000000000000E+0002
Element 6: Non-Numeric Value     - $A1

FreeBASIC

FreeBASIC has a built-in Val() function which converts numeric strings to doubles. However, it is not ideal for the present task since it will try to convert as much of the string as it can (so "123xyz" would convert to 123) and return 0 if a conversion on this basis is not possible (i.e. "xyz" would return 0).

I've therefore written a custom function which recognizes signed numbers in bases from 2 to 16 (but only integral numbers for bases other than 10). For base 10, it will treat "123." or ".123" as numbers but not ".". It doesn't recognize scientific notation but does recognize the integral prefixes &H, &O and &B if bases 16, 8 or 2 respectively are specified.

' FB 1.05.0 Win64

Dim Shared symbols(0 To 15) As UByte
For i As Integer = 48 to 57
  symbols(i - 48) = i
Next
For i As Integer = 97 to 102
  symbols(i - 87) = i
Next

Const plus  As UByte = 43
Const minus As Ubyte = 45
Const dot   As UByte = 46

Function isNumeric(s As Const String, base_ As Integer = 10) As Boolean
  If s = "" OrElse s = "."  OrElse s = "+" OrElse s = "-" Then Return False
  Err = 0 

  If base_ < 2 OrElse base_ > 16 Then
    Err = 1000
    Return False
  End If

  Dim t As String = LCase(s)

  If (t[0] = plus) OrElse (t[0] = minus) Then
     t = Mid(t, 2)
  End If

  If Left(t, 2) = "&h" Then
    If base_ <> 16 Then Return False
    t = Mid(t, 3)
  End if

  If Left(t, 2) = "&o" Then
    If base_ <> 8 Then Return False
    t = Mid(t, 3)
  End if

  If Left(t, 2) = "&b" Then
    If base_ <> 2 Then Return False
    t = Mid(t, 3)
  End if

  If Len(t) = 0 Then Return False
  Dim As Boolean isValid, hasDot = false
  
  For i As Integer = 0 To Len(t) - 1
    isValid = False

    For j As Integer = 0 To base_ - 1
      If t[i] = symbols(j) Then
        isValid = True
        Exit For
      End If
      If t[i] = dot Then
        If CInt(Not hasDot) AndAlso (base_ = 10) Then
          hasDot = True 
          IsValid = True
          Exit For
        End If
        Return False ' either more than one dot or not base 10
      End If
    Next j

    If Not isValid Then Return False
  Next i

  Return True 
End Function

Dim s As String
s = "1234.056789"
Print s, " (base 10) => "; isNumeric(s)
s = "1234.56"
Print s, " (base 7)  => "; isNumeric(s, 7) 
s = "021101"
Print s, " (base 2)  => "; isNumeric(s, 2)  
s = "Dog"
Print s, " (base 16) => "; isNumeric(s, 16)  
s = "Bad125"
Print s, " (base 16) => "; isNumeric(s, 16)  
s = "-0177"
Print s, " (base 8)  => "; isNumeric(s, 8)
s = "+123abcd.ef"
Print s, " (base 16) => "; isNumeric(s, 8)
s = "54321"
Print s, " (base 6)  => "; isNumeric(s, 6)
s = "123xyz"
Print s, " (base 10) => "; isNumeric(s)
s = "xyz"
Print s, " (base 10) => "; isNumeric(s)
Print
Print "Press any key to quit"
Sleep

Output:

1234.056789    (base 10) => true
1234.56        (base 7)  => false
021101         (base 2)  => false
Dog            (base 16) => false
Bad125         (base 16) => true
-0177          (base 8)  => true
+123abcd.ef    (base 16) => false
54321          (base 6)  => true
123xyz         (base 10) => false
xyz            (base 10) => false

FutureBasic

include "NSLog.incl"

local fn StringIsNumeric( string as CFStringRef ) as BOOL
  BOOL flag = NO
  ScannerRef scanner = fn ScannerWithString( string )
  if ( fn ScannerScanFloat( scanner, NULL ) )
    flag = fn ScannerIsAtEnd( scanner )
  end if
end fn = flag

NSLog(@"%d",fn StringIsNumeric( @"1.23" ))
NSLog(@"%d",fn StringIsNumeric( @"-123.4e5" ))
NSLog(@"%d",fn StringIsNumeric( @"alpha" ))

HandleEvents

Output:

1
1
0

Gambas

Public Sub Form_Open()
Dim sAnswer, sString As String

sString = Trim(InputBox("Enter as string", "String or Numeric"))

If IsNumber(sString) Then sAnswer = "'" & sString & "' is numeric" Else sAnswer = "'" & sString & "' is a string"
Print sAnswer

End

Output:

'Charlie' is a string
'-00.256666' is numeric

Go

This uses a library function to meet the task's requirements:

package main

import (
    "fmt"
    "strconv"
)

func isNumeric(s string) bool {
    _, err := strconv.ParseFloat(s, 64)
    return err == nil
}

func main() {
    fmt.Println("Are these strings numeric?")
    strings := []string{"1", "3.14", "-100", "1e2", "NaN", "rose"}
    for _, s := range strings {
        fmt.Printf("  %4s -> %t\n", s, isNumeric(s))
    }
}

Output:

Are these strings numeric?
     1 -> true
  3.14 -> true
  -100 -> true
   1e2 -> true
   NaN -> true
  rose -> false

This uses both a library function and a custom one but only checks for integerness:

package main

import (
    "fmt"
    "strconv"
    "unicode"
)

func isInt(s string) bool {
    for _, c := range s {
        if !unicode.IsDigit(c) {
            return false
        }
    }
    return true
}

func main() {
    fmt.Println("Are these strings integers?")
    v := "1"
    b := false
    if _, err := strconv.Atoi(v); err == nil {
        b = true
    }
    fmt.Printf("  %3s -> %t\n", v, b)
    i := "one"
    fmt.Printf("  %3s -> %t\n", i, isInt(i))
}

Output:

Are these strings integers?
    1 -> true
  one -> false

Groovy

Use the positional parser in java.text.NumberFormat. If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number.

def isNumeric = {
    def formatter = java.text.NumberFormat.instance
    def pos = [0] as java.text.ParsePosition
    formatter.parse(it, pos)
    
    // if parse position index has moved to end of string
    // them the whole string was numeric
    pos.index == it.size()
}

Test Program:

println isNumeric('1')
println isNumeric('-.555')
println isNumeric('1,000,000')
println isNumeric(' 1 1 1 1 ')
println isNumeric('abcdef')

Output:

true
true
true
false
false

Haskell

This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type with read or reads, and handle parsing failure appropriately.

The task doesn't define which strings are considered "numeric", so we do Integers and Doubles, which should catch the most common cases (including hexadecimal 0x notation):

isInteger s = case reads s :: [(Integer, String)] of
  [(_, "")] -> True
  _         -> False

isDouble s = case reads s :: [(Double, String)] of
  [(_, "")] -> True
  _         -> False

isNumeric :: String -> Bool
isNumeric s = isInteger s || isDouble s

One can easily add isRational, isComplex etc. following the same pattern.

Another way would be to use the Data.Char module, allowing code such as:

areDigits = all isDigit
isDigit  selects ASCII digits i.e. '0'..'9'
isOctDigit selects '0'..'7'
isHexDigit selects '0'..'9','A'..'F','a'..'f'

so read s::Int (for instance) could be reliably used if string s passed these tests.

Haxe

Haxe has a built-in function that will convert a string to an integer, so we can use that to determine if the string is numeric or not.

static function isNumeric(n:String):Bool
{
	if (Std.parseInt(n) != null) //Std.parseInt converts a string to an int
        {
		return true; //as long as it results in an integer, the function will return true
	}
        else
        {
		return false;
	}
}

HicEst

                              !    = bin + 2*int + 4*flt + 8*oct +16*hex + 32*sci
   isNumeric("1001")          ! 27 =  1       1       0       1       1        0
   isNumeric("123")           ! 26 =  0       1       0       1       1        0
   isNumeric("1E78")          ! 48 =  0       0       0       0       1        1
   isNumeric("-0.123")        !  4 =  0       0       1       0       0        1
   isNumeric("-123.456e-78")  ! 32 =  0       0       0       0       0        1
   isNumeric(" 123")          !  0: leading blank
   isNumeric("-123.456f-78")  !  0: illegal character f


FUNCTION isNumeric(string)    ! true ( > 0 ), no leading/trailing blanks
   CHARACTER string
   b = INDEX(string, "[01]+", 128, Lbin)                ! Lbin returns length found
   i = INDEX(string, "-?\d+", 128, Lint)                ! regular expression: 128
   f = INDEX(string, "-?\d+\.\d*", 128, Lflt)
   o = INDEX(string, "[0-7]+",    128, Loct)
   h = INDEX(string, "[0-9A-F]+", 128, Lhex)            ! case sensitive: 1+128
   s = INDEX(string, "-?\d+\.*\d*E[+-]*\d*", 128, Lsci)
   IF(anywhere) THEN     ! 0 (false) by default
     isNumeric = ( b > 0 ) + 2*( i > 0 ) + 4*( f > 0 ) + 8*( o > 0 ) + 16*( h > 0 ) + 32*( s > 0 )
   ELSEIF(boolean) THEN  ! 0 (false) by default
     isNumeric = ( b + i + f + o + h + s ) > 0 ! this would return 0 or 1
   ELSE
     L = LEN(string)
     isNumeric = (Lbin==L) + 2*(Lint==L) + 4*(Lflt==L) + 8*(Loct==L) + 16*(Lhex==L) + 32*(Lsci==L)
   ENDIF
 END

i

concept numeric(n) {
	number(n)
	errors {
		print(n, "  is not numeric!")
		return
	}
	print(n, "  is numeric :)")
}

software {
	numeric("1200")
	numeric("3.14")
	numeric("3/4")
	numeric("abcdefg")
	numeric("1234test")
}

Icon and Unicon

The code writes a printable image of x whatever type it is and a statement about whether it is numeric or not. Icon and Unicon use success and failure instead of boolean functions, numeric(x) is built-in and returns x or fails.

write(image(x), if numeric(x) then " is numeric." else " is not numeric")

IDL

function isnumeric,input
  on_ioerror, false
  test = double(input)
  return, 1
  false: return, 0
end

Could be called like this:

if isnumeric('-123.45e-2') then print, 'yes' else print, 'no'
; ==> yes
if isnumeric('picklejuice') then print, 'yes' else print, 'no'
; ==> no

Insitux

Non-null and non-false values are truthy in Insitux. The operation to-num returns null if it is unable to parse its string parameter, else the parsed number. The operation bool is unnecessary in most situations, but is composed with to-num here to satisfy the task specification.

> (var numeric? (comp to-num bool))
(comp to-num bool)

> (numeric? "123")
true

> (numeric? "0x25")
true

> (numeric? "0b0101")
true

> (numeric? "hello")
false

> (numeric? "123x456")
false

J

isNumeric=: _ ~: _ ". ]
isNumericScalar=: 1 -: isNumeric
TXT=: ,&' a scalar numeric value.' &.> ' is not';' represents'
sayIsNumericScalar=: , TXT {::~ isNumericScalar

Examples of use:

   isNumeric '152'
1
   isNumeric '152 -3.1415926 Foo123'
1 1 0
   isNumeric '42 foo42 4.2e1 4200e-2 126r3 16b2a 42foo'
1 0 1 1 1 1 0
   isNumericScalar '152 -3.1415926 Foo123'
0
   sayIsNumericScalar '-3.1415926'
-3.1415926 represents a scalar numeric value.

Java

Typically, you would use the 'parse' methods from either the Integer, Long, Float, or Double class,
which will throw a NumberFormatException for ill-formed values.
For example

Integer.parseInt("12345")

Float.parseFloat("123.456")

The performance mark is somewhat negligible between a try-block and custom methods.

public static void main(String[] args) {
    String value;
    value = "1234567";
    System.out.printf("%-10s %b%n", value, isInteger(value));
    value = "12345abc";
    System.out.printf("%-10s %b%n", value, isInteger(value));
    value = "-123.456";
    System.out.printf("%-10s %b%n", value, isFloatingPoint(value));
    value = "-.456";
    System.out.printf("%-10s %b%n", value, isFloatingPoint(value));
    value = "123.";
    System.out.printf("%-10s %b%n", value, isFloatingPoint(value));
    value = "123.abc";
    System.out.printf("%-10s %b%n", value, isFloatingPoint(value));
}

static boolean isInteger(String string) {
    String digits = "0123456789";
    for (char character : string.toCharArray()) {
        if (!digits.contains(String.valueOf(character)))
            return false;
    }
    return true;
}

static boolean isFloatingPoint(String string) {
    /* at least one decimal-point */
    int indexOf = string.indexOf('.');
    if (indexOf == -1)
        return false;
    /* assure only 1 decimal-point */
    if (indexOf != string.lastIndexOf('.'))
        return false;
    if (string.charAt(0) == '-' || string.charAt(0) == '+') {
        string = string.substring(1);
        indexOf--;
    }
    String integer = string.substring(0, indexOf);
    if (!integer.isEmpty()) {
        if (!isInteger(integer))
            return false;
    }
    String decimal = string.substring(indexOf + 1);
    if (!decimal.isEmpty())
        return isInteger(decimal);
    return true;
}

1234567    true
12345abc   false
-123.456   true
-.456      true
123.       true
123.abc    false

It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. If non-numeric strings are common, you're going to see a huge performance hit.

public boolean isNumeric(String input) {
  try {
    Integer.parseInt(input);
    return true;
  }
  catch (NumberFormatException e) {
    // s is not numeric
    return false;
  }
}

Alternative 1 : Check that each character in the string is number. Note that this will only works for integers.

private static final boolean isNumeric(final String s) {
  if (s == null || s.isEmpty()) return false;
  for (int x = 0; x < s.length(); x++) {
    final char c = s.charAt(x);
    if (x == 0 && (c == '-')) continue;  // negative
    if ((c >= '0') && (c <= '9')) continue;  // 0 - 9
    return false; // invalid
  }
  return true; // valid
}

Alternative 2 : use a regular expression (a more elegant solution).

public static boolean isNumeric(String inputData) {
  return inputData.matches("[-+]?\\d+(\\.\\d+)?");
}

Alternative 3 : use the positional parser in the java.text.NumberFormat object (a more robust solution). If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number.

public static boolean isNumeric(String inputData) {
  NumberFormat formatter = NumberFormat.getInstance();
  ParsePosition pos = new ParsePosition(0);
  formatter.parse(inputData, pos);
  return inputData.length() == pos.getIndex();
}

Alternative 4 : use the java.util.Scanner object. Very useful if you have to scan multiple entries.

public static boolean isNumeric(String inputData) {
  Scanner sc = new Scanner(inputData);
  return sc.hasNextInt();
}

Scanner also has similar methods for longs, shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well as methods for integral types where you may input a base/radix other than 10 (10 is the default, which can be changed using the useRadix method).

JavaScript

A far better validator can be found on StackOverflow[1]

function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}
var value = "123.45e7"; // Assign string literal to value
if (isNumeric(value)) {
  // value is a number
}
//Or, in web browser in address field:
//  javascript:function isNumeric(n) {return !isNaN(parseFloat(n)) && isFinite(n);}; value="123.45e4"; if(isNumeric(value)) {alert('numeric')} else {alert('non-numeric')}

jq

In versions of jq that support try/catch, the simplest way to test if a string can be parsed as a number is:

try tonumber catch false

The above expression will emit the corresponding number, or false if there is none. Here then is a boolean filter which will also emit true for each input that is a number:

def is_numeric: true and try tonumber catch false;

Julia

The function isnumber tests for strings that parse directly to numbers. This test excludes symbols, such as π and 1 + 1, that evaluate to numbers as well as certain elaborate numbers (large integers, rationals and complex numbers) whose literals parse to expressions that must be evaluated to yield numbers.

using Printf

isnumber(s::AbstractString) = tryparse(Float64, s) isa Number

tests = ["1", "-121", "one", "pi", "1 + 1", "NaN", "1234567890123456789", "1234567890123456789123456789",
        "1234567890123456789123456789.0", "1.3", "1.4e10", "Inf", "1//2", "1.0 + 1.0im"]

for t in tests
    fl = isnumber(t) ? "is" : "is not"
    @printf("%35s %s a direct numeric literal.\n", t, fl)
end

Output:

                                  1 is a direct numeric literal.
                               -121 is a direct numeric literal.
                                one is not a direct numeric literal.
                                 pi is not a direct numeric literal.
                              1 + 1 is not a direct numeric literal.
                                NaN is a direct numeric literal.
                1234567890123456789 is a direct numeric literal.
       1234567890123456789123456789 is a direct numeric literal.
     1234567890123456789123456789.0 is a direct numeric literal.
                                1.3 is a direct numeric literal.
                             1.4e10 is a direct numeric literal.
                                Inf is a direct numeric literal.
                               1//2 is not a direct numeric literal.
                        1.0 + 1.0im is not a direct numeric literal.

Kotlin

// version 1.1

fun isNumeric(input: String): Boolean =
    try {
        input.toDouble()
        true
    } catch(e: NumberFormatException) {
        false
    }

fun main(args: Array<String>) {
    val inputs = arrayOf("152", "-3.1415926", "Foo123", "-0", "456bar", "1.0E10")
    for (input in inputs) println("$input is ${if (isNumeric(input)) "numeric" else "not numeric"}")
}

Output:

152 is numeric
-3.1415926 is numeric
Foo123 is not numeric
-0 is numeric
456bar is not numeric
1.0E10 is numeric

LabVIEW

This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.

Lasso

Works with: Lasso version 8 & 9

local(str='12345')
string_isNumeric(#str) // true

Works with: Lasso version 9

'12345'->isdigit // true
'1X34Q'->isdigit // false

Liberty BASIC

DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0"
DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"


while n$ <> "end"
    read n$
    print n$, IsNumber(n$)
wend
end

function IsNumber(string$)
    on error goto [NotNumber]
    string$ = trim$(string$)
    'check for float overflow
    n = val(string$)

    'assume it is number and try to prove wrong
    IsNumber = 1
    for i = 1 to len(string$)
        select case mid$(string$, i, 1)
            case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
                HasNumeric = 1 'to check if there are any digits
            case "e", "E"
                '"e" must not occur more than once
                'must not occur before digits

                if HasE > 0 or HasNumeric = 0 then
                    IsNumber = 0
                    exit for
                end if
                HasE = i 'store position of "e"
                HasNumeric = 0 'needs numbers after "e"
            case "-", "+"
                'must be either first character or immediately after "e"
                '(HasE = 0 if no occurrences yet)
                if HasE <> i-1 then
                    IsNumber = 0
                    exit for
                end if
            case "."
                'must not have previous points and must not come after "e"
                if HasE <> 0 or HasPoint <> 0 then
                    IsNumber = 0
                    exit for
                end if
                HasPoint = 1
            case else
                'no other characters allowed
                IsNumber = 0
                exit for
        end select
    next i
    'must have digits
    if HasNumeric = 0 then IsNumber = 0
    [NotNumber]
end function

Lisaac

"123457".is_integer.println;
// write TRUE on stdin

Logo

show number? "-1.23    ; true

Lua

This will also accept strings like "0xFF" or "314.16e-2" as numbers.

if tonumber(a) ~= nil then
   --it's a number
end;

M2000 Interpreter

We have to define our IsNumber() Version 2 handle decimal point character. For code M2000 use dot, but for input and output use the user specified decimal point, from OS. Function Str$(1.2) return a string with a dot always, but if we place a second parameter this change. Print str$(1.2, "") maybe return 1,2 and nor 1.2. Print str$(1.2, "#.00") maybe return 1.20 or 1,20. The reverse function is Val() which can take more characters so A Val("121mm") is 121, and with a second parameter we can interpret properly the decimal dot: Print Val("1.2", ".") always return 1.2 double. Print Val("1,2", ",")=1.2 return true, 1.2 is a m2000 number literal and always has a dot.

\\ version 2
Module Checkit {
      function global isNumber(a$, de$=".") {
            =false=true  ' return boolean
            if de$="" then de$=str$(.1,".")  ' get current decimal point character
            a$=trim$(ucase$(a$))
            m=len(a$)
            if m=0 then exit
            c$=filter$(a$,"0123456789")
            if c$ = "" then {
                  =true
            } else.if m>1 then {
                  \ may have -+ and ,      
                  if m=2 then {
                        if not c$~"[-+\"+de$+"]" then break
                  } else {
                        if left$(c$,1 ) ~"[+-]" then c$=mid$(c$, 2)
                        if not (c$=de$ or c$=de$+"E" or c$ ~ de$+"E[+-]") then break
                        if c$ ~ de$+"E[+-]" then if not (instr(a$,"E+")>0 or instr(a$,"E-")>0) then break
                  }
                 if de$<>"." then  a$=replace$(de$, ".", a$, 1,1)
                 try {inline "a="+a$+"=="+a$}
                 if valid(a) then =a = true=true  ' return boolean
             }    
      }
      Print isNumber("+1"), isnumber("-1"), isNumber("1+")=false, isnumber("1-")=false
      Print isNumber(",1",","), isnumber("1,",","), isNumber(",0",","), isnumber("0,", ",")
      Print isNumber(".1"), isnumber("1."), isNumber(".0"), isnumber("0.")
      Print isNumber("+.1"), isnumber("-1."), isNumber(".12e+232"), isnumber("0.122e10")
      Print isNumber("+.1a")=false, isnumber("asasa1212")=false, isNumber("1.2e43+23")=false, isnumber("0.122e10")
      Print isNumber("1221.211.1221")=false, isnumber("1221e1212")=false, isNumber("1.2e4323")=false, isnumber("-.122e-10")
}
Checkit

From rev.31 Version 9.3 Val function update, to include a more quick version of above. We have to specify the dot char or write any two or more chars for dot to get integer part. Val function return number and in third argument (passing by reference by default) return first position in string after number. If string is empty or have no number then position is -1. If a number found position is >1. Leading spaces trimmed.

Function IsNumeric(a$) {
      def m
      =val(false->boolean)
      Try {
            if islet then {
                  z=val(a$,letter$, m)
            } else.if isnum then {
                  z=val(a$,number, m)
            } else z=val(a$,"", m)
            =m>len(a$)
      }
}
Function IsIntegerNumeric(a$) {
      def m
      =val(false->boolean)
      Try {
            z=val(a$,"Int", m)
            =m>len(a$)
      }
}

Locale 1033 ' to use . as decimal, else we have to place 1033 or "." as second parameter

Print isNumeric("+1"), isNumeric("-1"), isNumeric("1+")=false, isNumeric("1-")=false
Print isNumeric(",1",","), isNumeric("1,",","), isNumeric(",0",","), isNumeric("0,", ",")
Print isNumeric(".1"), isNumeric("1."), isNumeric(".0"), isNumeric("0.")
Print isNumeric("+.1"), isNumeric("-1."), isNumeric(".12e+232"), isNumeric("0.122e10")
Print isNumeric("+.1a")=false, isNumeric("asasa1212")=false, isNumeric("1.2e43+23")=false, isNumeric("0.122e10")
Print isNumeric("1221.211.1221")=false, isNumeric("1221e1212")=false, isNumeric("1.2e4323")=false, isNumeric("-.122e-10")

Maple

isNumeric := proc(s)
	try
		if type(parse(s), numeric) then
			printf("The string is numeric."):
		else
			printf("The string is not numeric."):
		end if:
	catch:
		printf("The string is not numeric."):
	end try:
end proc:

Mathematica / Wolfram Language

NumberQ[ToExpression["02553352000242"]]

MATLAB

  function r = isnum(a)
    r = ~isnan(str2double(a))
  end 

% tests
disp(isnum(123)) % 1
disp(isnum("123")) % 1
disp(isnum("foo123")) % 0
disp(isnum("123bar")) % 0
disp(isnum("3.1415")) % 1

Maxima

numberp(parse_string("170141183460469231731687303715884105727"));

MAXScript

fn isNumeric str =
(
    try
    (
        (str as integer) != undefined
    )
    catch(false)
)

isNumeric "123"

min

Works with: min version 0.19.3

(
  dup (((int integer?) (pop false)) try) dip
  ((float float?) (pop false)) try or
) :numeric?

MiniScript

We rely on conversion to number returning a nonzero number, plus special checks for zero strings. Note that the val function is forgiving about additional characters after the number, so our function is too.

isNumeric = function(s)
    return s == "0" or s == "-0" or val(s) != 0
end function

print isNumeric("0")
print isNumeric("42")
print isNumeric("-3.14157")
print isNumeric("5@*#!")
print isNumeric("spam")

Output:

MIPS Assembly

# $a0 char val
# $a1 address pointer
# $a2 PERIOD_HIT_FLAG
# $a3 HAS_DIGITS_FLAG

.data 
			### CHANGE THIS STRING TO TEST DIFFERENT ONES... ###
	string: .asciiz "-.1236"  
	s_false: .asciiz "False"
	s_true: .asciiz "True"
.text
main:
	set_up: #test for 0th char == 45 or 46 or 48...57
		la $a1,string
		lb $a0,($a1)
		beq $a0,45,loop # == '-'
		beq $a0,46,loop # == '.'
		blt $a0,48,exit_false # isn't below the ascii range for chars '0'...'9'
		bgt $a0,57,exit_false # isn't above the ascii range for chars '0'...'9'
	loop:
		addi $a1,$a1,1
		lb $a0,($a1)
		beqz $a0,exit_true # test for \0 null char
		beq $a0,46,period_test #test for a duplicate period
		blt $a0,48,exit_false  #test for 
		bgt $a0,57,exit_false
		la $a3,1 #set the HAS_DIGITS flag. This line is only reached because the
			 #    tests for period and - both jump back to start. 
		j loop
	
exit_true:
	beqz $a3,exit_false
	la $a0,s_true
	la $v0,4
	syscall

	li $v0,10
	syscall	

exit_false:
	la $a0,s_false
	la $v0,4
	syscall
	
	li $v0,10
	syscall
	
period_test:
	beq $a2,1,exit_false
	li $a2,1
	j loop

Mirah

import java.text.NumberFormat
import java.text.ParsePosition
import java.util.Scanner

# this first example relies on catching an exception, 
# which is bad style and poorly performing in Java
def is_numeric?(s:string)
    begin
        Double.parseDouble(s)
        return true
    rescue
        return false
    end
end

puts '123   is numeric' if is_numeric?('123')
puts '-123  is numeric' if is_numeric?('-123')
puts '123.1 is numeric' if is_numeric?('123.1')

puts 'nil   is not numeric' unless is_numeric?(nil)
puts "''    is not numeric" unless is_numeric?('')
puts 'abc   is not numeric' unless is_numeric?('abc')
puts '123-  is not numeric' unless is_numeric?('123-')
puts '1.2.3 is not numeric' unless is_numeric?('1.2.3')


# check every element of the string
def is_numeric2?(s: string) 
    if (s == nil || s.isEmpty()) 
        return false 
    end 
    if (!s.startsWith('-')) 
        if s.contains('-')
            return false 
        end
    end 
    
    0.upto(s.length()-1) do |x|
        c = s.charAt(x)
        if ((x == 0) && (c == '-'.charAt(0)))
            # negative number
        elsif (c == '.'.charAt(0))
            if (s.indexOf('.', x) > -1) 
                return false # more than one period
            end        
        elsif (!Character.isDigit(c))
            return false
        end
    end 
    true
end


puts '123   is numeric' if is_numeric2?('123')
puts '-123  is numeric' if is_numeric2?('-123')
puts '123.1 is numeric' if is_numeric2?('123.1')

puts 'nil   is not numeric' unless is_numeric2?(nil)
puts "''    is not numeric" unless is_numeric2?('')
puts 'abc   is not numeric' unless is_numeric2?('abc')
puts '123-  is not numeric' unless is_numeric2?('123-')
puts '1.2.3 is not numeric' unless is_numeric2?('1.2.3')



# use a regular  expression 
def is_numeric3?(s:string)
  s == nil || s.matches("[-+]?\\d+(\\.\\d+)?")
end

puts '123   is numeric' if is_numeric3?('123')
puts '-123  is numeric' if is_numeric3?('-123')
puts '123.1 is numeric' if is_numeric3?('123.1')

puts 'nil   is not numeric' unless is_numeric3?(nil)
puts "''    is not numeric" unless is_numeric3?('')
puts 'abc   is not numeric' unless is_numeric3?('abc')
puts '123-  is not numeric' unless is_numeric3?('123-')
puts '1.2.3 is not numeric' unless is_numeric3?('1.2.3')


#  use the positional parser in the java.text.NumberFormat object 
# (a more robust solution). If, after parsing, the parse position is at 
# the end of the string, we can deduce that the entire string was a 
# valid number.
def is_numeric4?(s:string) 
    return false if s == nil    
    formatter = NumberFormat.getInstance()
    pos = ParsePosition.new(0)
    formatter.parse(s, pos)
    s.length() == pos.getIndex()
end


puts '123   is numeric' if is_numeric4?('123')
puts '-123  is numeric' if is_numeric4?('-123')
puts '123.1 is numeric' if is_numeric4?('123.1')

puts 'nil   is not numeric' unless is_numeric4?(nil)
puts "''    is not numeric" unless is_numeric4?('')
puts 'abc   is not numeric' unless is_numeric4?('abc')
puts '123-  is not numeric' unless is_numeric4?('123-')
puts '1.2.3 is not numeric' unless is_numeric4?('1.2.3')


# use the java.util.Scanner object. Very useful if you have to 
# scan multiple entries. Scanner also has similar methods for longs, 
# shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well 
# as methods for integral types where you may input a base/radix other than 
# 10 (10 is the default, which can be changed using the useRadix method).
def is_numeric5?(s:string)
    return false if s == nil
    Scanner sc = Scanner.new(s)
    sc.hasNextDouble()
end

puts '123   is numeric' if is_numeric5?('123')
puts '-123  is numeric' if is_numeric5?('-123')
puts '123.1 is numeric' if is_numeric5?('123.1')

puts 'nil   is not numeric' unless is_numeric5?(nil)
puts "''    is not numeric" unless is_numeric5?('')
puts 'abc   is not numeric' unless is_numeric5?('abc')
puts '123-  is not numeric' unless is_numeric5?('123-')
puts '1.2.3 is not numeric' unless is_numeric5?('1.2.3')

mIRC Scripting Language

Works with: mIRC

var %value = 3
if (%value isnum) {
  echo -s %value is numeric.
}

Modula-3

MODULE Numeric EXPORTS Main;

IMPORT IO, Fmt, Text;

PROCEDURE isNumeric(s: TEXT): BOOLEAN =
  BEGIN
    FOR i := 0 TO Text.Length(s) DO
      WITH char = Text.GetChar(s, i) DO
        IF i = 0 AND char = '-' THEN
          EXIT;
        END;
        IF char >= '0' AND char <= '9' THEN
          EXIT;
        END;
        RETURN FALSE;
      END;
    END;
    RETURN TRUE;
  END isNumeric;      

BEGIN
  IO.Put("isNumeric(152) = " & Fmt.Bool(isNumeric("152")) & "\n");
  IO.Put("isNumeric(-3.1415926) = " & Fmt.Bool(isNumeric("-3.1415926")) & "\n");
  IO.Put("isNumeric(Foo123) = " & Fmt.Bool(isNumeric("Foo123")) & "\n");
END Numeric.

Output:

isNumeric(152) = TRUE
isNumeric(-3.1415926) = TRUE
isNumeric(Foo123) = FALSE

MUMPS

In MUMPS, strings are automatically converted to numbers when a unary or binary arithmetic operator works upon them. If there are no leading digits, a string converts to zero. If there a string of digits followed by an "e" or an "E" followed in turn by more digits, the numbers after the letter are treated as an exponent.

Examples from command line:

USER>WRITE +"1"
1
USER>WRITE +"1A"
1
USER>WRITE +"A1"
0
USER>WRITE +"1E"
1
USER>WRITE +"1E2"
100
USER>WRITE +"1EA24"
1
USER>WRITE +"1E3A"
1000
USER>WRITE +"1E-3"
.001

There is a function, $ISVALIDNUM, to do the testing.

USER>WRITE $SELECT($ISVALIDNUM("123"):"Valid",1:"Invalid"),!
Valid
 
USER>WRITE $SELECT($ISVALIDNUM("a123"):"Valid",1:"Invalid"),!
Invalid
 
USER>WRITE $SELECT($ISVALIDNUM("123a"):"Valid",1:"Invalid"),!
Invalid

USER>WRITE $SELECT($ISVALIDNUM("123e4"):"Valid",1:"Invalid"),!
Valid

Nanoquery

def isNum(str)
    try
        double(str)
        return true
    catch
        return false
    end
end

Nemerle

using System;
using System.Console;

module IsNumeric
{
    IsNumeric( input : string) : bool
    {
        mutable meh = 0.0;  // I don't want it, not going to use it, why force me to declare it?
        double.TryParse(input, out meh)
    }
    
    Main() : void
    {
        def num = "-1.2345E6";
        def not = "abc45";
        WriteLine($"$num is numeric: $(IsNumeric(num))");
        WriteLine($"$not is numeric: $(IsNumeric(not))");
    }
}

NetRexx

/* NetRexx */
options replace format comments java crossref symbols nobinary

numeric digits 20

loop n_ over getTestData()
  -- could have used n_.datatype('N') directly here...
  if isNumeric(n_) then msg = 'numeric'
                   else msg = 'not numeric'
  say ('"'n_'"').right(25)':' msg
  end n_

return

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Pointless in NetRexx; the DATATYPE built-in-function is more powerful!
method isNumeric(testString) public static returns boolean
  return testString.datatype('N')

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method getTestData() private static returns Rexx[]
  
  -- Coercing numbers into the Rexx type has the effect of converting them to strings.
  -- NetRexx will still perform arithmetic on Rexx strings if those strings represent numbers.
  -- Notice that whitespace between the sign and the number are ignored even when inside a string constant
  testData = [ Rexx -
    ' one and a half',   1,   1.5,    1.5e+27, '   1 ', '  1.5 ', '  1.5e+27 ', -
    '-one and a half', - 1, - 1.5,  - 1.5e-27, ' - 1 ', '- 1.5 ', '- 1.5e-27 ', -
    '+one and a half', + 1, + 1.5,  + 1.5e+27, ' + 1 ', '+ 1.5 ', '+ 1.5e+27 ', -
    'Math Constants', -
     Math.PI,  Math.E, -
    -Math.PI, -Math.E, -
    +Math.PI, +Math.E, -
    'Numeric Constants', -
    Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY -
    ]
  return testData

Output:

        " one and a half": not numeric
                      "1": numeric
                    "1.5": numeric
                "1.5e+27": numeric
                  "   1 ": numeric
                 "  1.5 ": numeric
             "  1.5e+27 ": numeric
        "-one and a half": not numeric
                     "-1": numeric
                   "-1.5": numeric
               "-1.5E-27": numeric
                  " - 1 ": numeric
                 "- 1.5 ": numeric
             "- 1.5e-27 ": numeric
        "+one and a half": not numeric
                      "1": numeric
                    "1.5": numeric
                "1.5E+27": numeric
                  " + 1 ": numeric
                 "+ 1.5 ": numeric
             "+ 1.5e+27 ": numeric
         "Math Constants": not numeric
      "3.141592653589793": numeric
      "2.718281828459045": numeric
     "-3.141592653589793": numeric
     "-2.718281828459045": numeric
      "3.141592653589793": numeric
      "2.718281828459045": numeric
      "Numeric Constants": not numeric
                    "NaN": not numeric
               "Infinity": not numeric
               "Infinity": not numeric

Nim

import strutils

proc isNumeric(s: string): bool =
  try:
    discard s.parseFloat()
    result = true
  except ValueError:
    result = false

const Strings = ["1", "3.14", "-100", "1e2", "Inf", "rose"]

for s in Strings:
  echo s, " is ", if s.isNumeric(): "" else: "not ", "numeric"

We could prefer to use the “parsutils” module which avoids the exception:

import parseutils

proc isNumeric(s: string): bool =
  var x: float
  s.parseFloat(x) == s.len

const Strings = ["1", "3.14", "-100", "1e2", "Inf", "rose"]

for s in Strings:
  echo s, " is ", if s.isNumeric(): "" else: "not ", "numeric"

Output:

1 is numeric
3.14 is numeric
-100 is numeric
1e2 is numeric
Inf is numeric
rose is not numeric

Nu

def is-numeric [] {try {into float | true} catch {false}}

["1" "12" "-3" "5.6" "-3.14" "one" "cheese"] | each {{k: $in, v: ($in | is-numeric)}}

Output:

╭───┬────────┬───────╮
│ # │   k    │   v   │
├───┼────────┼───────┤
│ 0 │ 1      │ true  │
│ 1 │ 12     │ true  │
│ 2 │ -3     │ true  │
│ 3 │ 5.6    │ true  │
│ 4 │ -3.14  │ true  │
│ 5 │ one    │ false │
│ 6 │ cheese │ false │
╰───┴────────┴───────╯

Objeck

class Numeric {
  function : Main(args : String[]) ~ Nil {
    if(args->Size() = 1) {
      IsNumeric(args[0])->PrintLine();
    };
  }

  function : IsNumeric(str : String) ~ Bool {
    return str->IsFloat();
  }
}

Objective-C

Works with: GCC

Works with: OpenStep

Works with: GNUstep

The NSScanner class supports scanning of strings for various types. The scanFloat method will return YES if the string is numeric, even if the number is actually too long to be contained by the precision of a float.

if( [[NSScanner scannerWithString:@"-123.4e5"] scanFloat:NULL] )
	NSLog( @"\"-123.4e5\" is numeric" );
else
	NSLog( @"\"-123.4e5\" is not numeric" );
if( [[NSScanner scannerWithString:@"Not a number"] scanFloat:NULL] )
	NSLog( @"\"Not a number\" is numeric" );
else
	NSLog( @"\"Not a number\" is not numeric" );
// prints: "-123.4e5" is numeric
// prints: "Not a number" is not numeric

The following function can be used to check if a string is numeric "totally"; this is achieved by checking if the scanner reached the end of the string after the float is parsed.

BOOL isNumeric(NSString *s)
{
   NSScanner *sc = [NSScanner scannerWithString: s];
   if ( [sc scanFloat:NULL] )
   {
      return [sc isAtEnd];
   }
   return NO;
}

If we want to scan by hand, we could use a function like the following, that checks if a number is an integer positive or negative number; spaces can appear at the beginning, but not after the number, and the '+' or '-' can appear only attached to the number ("+123" returns YES, but "+ 123" returns NO).

BOOL isNumericI(NSString *s)
{
   NSUInteger len = [s length];
   NSUInteger i;
   BOOL status = NO;
   
   for(i=0; i < len; i++)
   {
       unichar singlechar = [s characterAtIndex: i];
       if ( (singlechar == ' ') && (!status) )
       {
         continue;
       }
       if ( ( singlechar == '+' ||
              singlechar == '-' ) && (!status) ) { status=YES; continue; }
       if ( ( singlechar >= '0' ) &&
            ( singlechar <= '9' ) )
       {
          status = YES;
       } else {
          return NO;
       }
   }
   return (i == len) && status;
}

Here we assumed that in the internal encoding of a string (that should be Unicode), 1 comes after 0, 2 after 1 and so on until 9. Another way could be to get the C String from the NSString object, and then the parsing would be the same of the one we could do in standard C, so this path is not given.

OCaml

This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type and handle parsing failure appropriately.

The task doesn't define which strings are considered "numeric", so we do ints and floats, which should catch the most common cases:

let is_int s =
  try ignore (int_of_string s); true
  with _ -> false

let is_float s =
  try ignore (float_of_string s); true
  with _ -> false

let is_numeric s = is_int s || is_float s

Octave

The builtin function isnumeric return true (1) if the argument is a data of type number; the provided function isnum works the same for numeric datatype, while if another type is passed as argument, it tries to convert it to a number; if the conversion fails, it means it is not a string representing a number.

function r = isnum(a)
  if ( isnumeric(a) )
    r = 1;
  else
    r = ~isnan(str2double(a));
  endif
endfunction

% tests
disp(isnum(123))      % 1
disp(isnum("123"))    % 1
disp(isnum("foo123")) % 0
disp(isnum("123bar")) % 0
disp(isnum("3.1415")) % 1

Odin

package main

import "core:strconv"
import "core:fmt"

is_numeric :: proc(s: string) -> bool {
  _, ok := strconv.parse_f32(s)
  return ok
}

main :: proc() {
  strings := []string{"1", "3.14", "-100", "1e2", "Inf", "rose"}
  for s in strings {
    fmt.println(s, "is", is_numeric(s) ? "numeric" : "not numeric")
  }
}

/* Output:
1 is numeric
3.14 is numeric
-100 is numeric
1e2 is numeric
Inf is not numeric
rose is not numeric
*/

Oz

fun {IsNumeric S}
   {String.isInt S} orelse {String.isFloat S}
end

PARI/GP

isNumeric(s)={
  my(t=type(eval(s)));
  t == "t_INT" || t == "T_REAL"
};

Pascal

See Delphi or Free Pascal.

PeopleCode

Built-In Function
Syntax

IsNumber(Value)
Description

Use the IsNumber function to determine if Value contains a valid numeric value. Numeric characters include sign indicators and comma and period decimal points.
To determine if a value is a number and if it's in the user's local format, use the IsUserNumber function.

Parameters

Value
Specify a string you want to search to determine if it is a valid number.

Returns
A Boolean value: True if Value contains a valid numeric value, False otherwise.

Example

&Value = Get Field().Value; 
If IsNumber(&Value) Then 
   /* do numeric processing */ 
Else 
   /* do non-numeric processing */ 
End-if;

Perl

Works with: Perl version 5.8

use Scalar::Util qw(looks_like_number);
print looks_like_number($str) ? "numeric" : "not numeric\n";

Works with: Perl version 5.8

Quoting from perlfaq4:

How do I determine whether a scalar is a number/whole/integer/float?

Assuming that you don't care about IEEE notations like "NaN" or "Infinity", you probably just want to use a regular expression.

if (/\D/)            { print "has nondigits\n" }
if (/^\d+\z/)         { print "is a whole number\n" }
if (/^-?\d+\z/)       { print "is an integer\n" }
if (/^[+-]?\d+\z/)    { print "is a +/- integer\n" }
if (/^-?\d+\.?\d*\z/) { print "is a real number\n" }
if (/^-?(?:\d+(?:\.\d*)?&\.\d+)\z/) { print "is a decimal number\n" }
if (/^([+-]?)(?=\d&\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?\z/)
                     { print "a C float\n" }

There are also some commonly used modules for the task. Scalar::Util (distributed with 5.8) provides access to Perl's internal function "looks_like_number" for determining whether a variable looks like a number. Data::Types exports functions that validate data types using both the above and other regular expressions. Thirdly, there is "Regexp::Common" which has regular expressions to match various types of numbers. Those three modules are available from the CPAN.

If you're on a POSIX system, Perl supports the "POSIX::strtod" function. Its semantics are somewhat cumbersome, so here's a "getnum" wrapper function for more convenient access. This function takes a string and returns the number it found, or "undef" for input that isn't a C float. The "is_numeric" function is a front end to "getnum" if you just want to say, Is this a float?

sub getnum {
    use POSIX;
    my $str = shift;
    $str =~ s/^\s+//;
    $str =~ s/\s+$//;
    $! = 0;
    my($num, $unparsed) = strtod($str);
    if (($str eq '') && ($unparsed != 0) && $!) {
        return undef;
    } else {
        return $num;
    }
}

sub is_numeric { defined getnum($_[0]) }

Or you could check out the String::Scanf module on the CPAN instead. The POSIX module (part of the standard Perl distribution) provides the "strtod" and "strtol" for converting strings to double and longs, respectively.

Phix

function isNumber(string s)
    return scanf(s,"%f")!={}
-- Alt: isNumberString(object s) and
--  return string(s) and scanf(s,"%f")!={}, or even
--  return string(s) and scanf(substitute(trim(s),",",""),"%f")!={}
end function
 
constant tests = {"#a","#A","0xA","0(16)A","#FF","255","0",
                  "0.","0.0","000.000","0e0","0e-2000"," ",
                  ".14",".05","-5.2","0xf","ten","1B","#1B",
                  " 12  ",trim(" 12  "),"1","0o16","0o18",
                  "0b10101111_11110000_11110000_00110011",
                  "1_000","50e","+123","+ 123","-0b10101",
                  "NaN","+.345","12..34","12e3.4","0-2",
                  "192.168.0.1","1.2e","1 2","12.34","",
                  "beef","#beef","1,000,000","Inf","1/2",
                  "1.5e+27","0x10.5","1."} 
 
sequence numeric = {},
         notnumb = {}
for i=1 to length(tests) do
    string ti = tests[i]
    if isNumber(ti) then
        numeric = append(numeric,ti)
    else
        notnumb = append(notnumb,ti)
    end if
end for
puts(1,"numeric: ")
pp(numeric,{pp_Indent,9})
puts(1,"\nnot numeric: ")
pp(notnumb,{pp_Indent,13})

Output:

numeric: {`#a`, `#A`, `0xA`, `0(16)A`, `#FF`, `255`, `0`, `0.0`, `000.000`,
          `0e0`, `0e-2000`, `.14`, `.05`, `-5.2`, `0xf`, `#1B`, `12`, `1`,
          `0o16`, `0b10101111_11110000_11110000_00110011`, `1_000`, `+123`,
          `-0b10101`, `+.345`, `12.34`, `#beef`, `1.5e+27`, `0x10.5`}

not numeric: {`0.`, ` `, `ten`, `1B`, ` 12  `, `0o18`, `50e`, `+ 123`,
              `NaN`, `12..34`, `12e3.4`, `0-2`, `192.168.0.1`, `1.2e`,
              `1 2`, ``, `beef`, `1,000,000`, `Inf`, `1/2`, `1.`}

Should you want to check for (eg) complex numbers, your best bet is to (also) invoke scanf() with several other different format strings such as "%f+%fi", "%f-%fj" (etc), until one works, or they all fail.

PHP

<?php
$string = '123';
if(is_numeric(trim($string))) {
}
?>

PicoLisp

The 'format' function can be used for that. It returns NIL if the given string is not a legal number

: (format "123")
-> 123

: (format "123a45")
-> NIL

: (format "-123.45" 4)
-> 1234500

Pike

the sscanf format %f will find any kind of number. the %s before and after make sure the number is not surrounded by other text.

int(0..1) is_number(string s)
{
    array test = array_sscanf(s, "%s%f%s");
    if (sizeof(test) == 3 && test[1] && !sizeof(test[0]) && !sizeof(test[2]) )
        return true;
    else
        return false;
}

string num = "-1.234"
is_number(num);
-> true

PL/I

is_numeric: procedure (text) returns (bit (1));
   declare text character (*);
   declare x float;

   on conversion go to done;

   get string(text) edit (x) (E(length(text),0));
   return ('1'b);

done:
   return ('0'b);
end is_numeric;

5                       '1'B 
6.7                     '1'B 
-8.9                    '1'B 
-4e3                    '1'B 
4A37                    '0'B

PL/SQL

FUNCTION IsNumeric( value IN VARCHAR2 )
RETURN BOOLEAN
IS
  help NUMBER;
BEGIN
  help := to_number( value );
  return( TRUE );
EXCEPTION
  WHEN others THEN
    return( FALSE );
END;

Value VARCHAR2( 10 ) := '123';
IF( IsNumeric( Value ) )
  THEN
    NULL;
END  IF;

Plain English

The following decider exists in the noodle To decide if a string is any numeric literal:
and is used to resolve the If clause If the string is any numeric literal, in this solution.

To run:
Start up.
Show whether "cat" is numeric.
Show whether "3" is numeric.
Show whether "+3" is numeric.
Show whether "-123" is numeric.
Show whether "123,456" is numeric.
Show whether "11/5" is numeric.
Show whether "-26-1/3" is numeric.
Show whether "+26-1/3" is numeric.
Show whether "1/0" is numeric. \in Plain English, 1/0 is 0. Don't tell the mathematicians!
Show whether "3.14159" is numeric. \floating point is not implemented in Plain English.
Wait for the escape key.
Shut down.

To show whether a string is numeric:
Write the string then " -> " on the console without advancing.
If the string is any numeric literal, write "yes" on the console; exit.
Write "no" on the console.

Output:

cat -> no
3 -> yes
+3 -> yes
-123 -> yes
123,456 -> no
11/5 -> yes
-26-1/3 -> yes
+26-1/3 -> yes
1/0 -> yes
3.14159 -> no

PowerShell

Note: PowerShell 1.0 does not support 'try' THis simply tries arithmetic with the argument and if that fails, false is returned.

function isNumeric ($x) {
    try {
        0 + $x | Out-Null
        return $true
    } catch {
        return $false
    }
}

But this one doesn't work for strings like "8." though a . is appended it returns true!

Alternatively, you can use the static System.Int32.TryParse() method in the .NET framework.

function isNumeric ($x) {
    $x2 = 0
    $isNum = [System.Int32]::TryParse($x, [ref]$x2)
    return $isNum
}

Prolog

Works with: SWI-Prolog version 7

The code:

numeric_string(String) :-
    atom_string(Atom, String),
    atom_number(Atom, _).

A predicate to test the code:

test_strings(Strings) :-
    forall( member(String, Strings),
            ( ( numeric_string(String)
              ->  Result = a
              ;   Result = 'not a' ),
              format('~w is ~w number.~n', [String, Result])
            )
          ).

Example of using the test predicate:

?- test_strings(["123", "0.123", "-123.1", "NotNum", "1."]).
123 is a number.
0.123 is a number.
-123.1 is a number.
NotNum is not a number.
1. is not a number.
true.

PureBasic

This routine parses the string to verify it's a number. It returns 1 if string is numeric, 0 if it is not. The character used as the decimal separator may be specified if desired.

Procedure IsNumeric(InString.s, DecimalCharacter.c = '.')
  #NotNumeric = #False
  #IsNumeric = #True
  
  InString = Trim(InString)
  Protected IsDecimal, CaughtDecimal, CaughtE
  Protected IsSignPresent, IsSignAllowed = #True, CountNumeric
  Protected *CurrentChar.Character = @InString
  
  While *CurrentChar\c
    Select *CurrentChar\c
      Case '0' To '9'
        CountNumeric + 1
        IsSignAllowed = #False
      Case DecimalCharacter
        If CaughtDecimal Or CaughtE Or CountNumeric = 0
          ProcedureReturn #NotNumeric
        EndIf
        
        CountNumeric = 0
        CaughtDecimal = #True
        IsDecimal = #True
      Case  '-', '+'
        If IsSignPresent Or Not IsSignAllowed: ProcedureReturn #NotNumeric: EndIf 
        IsSignPresent = #True
      Case 'E', 'e'
        If CaughtE Or CountNumeric = 0
          ProcedureReturn #NotNumeric
        EndIf
        
        CaughtE = #True
        CountNumeric = 0
        CaughtDecimal = #False
        IsSignPresent = #False
        IsSignAllowed = #True
      Default
        ProcedureReturn #NotNumeric
    EndSelect
    *CurrentChar + SizeOf(Character)
  Wend
  
  If CountNumeric = 0: ProcedureReturn #NotNumeric: EndIf
  ProcedureReturn #IsNumeric
EndProcedure

If OpenConsole()
  PrintN("'+3183.31151E+321' = " + Str(IsNumeric("+3183.31151E+321")))
  PrintN("'-123456789' = " + Str(IsNumeric("-123456789")))
  PrintN("'123.45.6789+' = " + Str(IsNumeric("123.45.6789+")))
  PrintN("'-e' = " + Str(IsNumeric("-e")))
  Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
  Input()
  CloseConsole()
EndIf

Output:

'+3183.31151E+321' = 1
'-123456789' = 1
'123.45.6789+' = 0
'-e' = 0

Python

Python: Simple int/float

def is_numeric(s):
    try:
        float(s)
        return True
    except (ValueError, TypeError):
        return False

is_numeric('123.0')

Or for positive integers only:

'123'.isdigit()

Python: Most numeric literals

Including complex, hex, binary, and octal numeric literals we get:

def is_numeric(literal):
    """Return whether a literal can be parsed as a numeric value"""
    castings = [int, float, complex,
        lambda s: int(s,2),  #binary
        lambda s: int(s,8),  #octal
        lambda s: int(s,16)] #hex
    for cast in castings:
        try:
            cast(literal)
            return True
        except ValueError:
            pass
    return False

Sample use, including value parsed, its type, and standard method str.isnumeric():

def numeric(literal):
    """Return value of numeric literal or None if can't parse a value"""
    castings = [int, float, complex,
        lambda s: int(s,2),  #binary
        lambda s: int(s,8),  #octal
        lambda s: int(s,16)] #hex
    for cast in castings:
        try:
            return cast(literal)
        except ValueError:
            pass
    return None


tests = [
    '0', '0.', '00', '123', '0123', '+123', '-123', '-123.', '-123e-4', '-.8E-04',
    '0.123', '(5)', '-123+4.5j', '0b0101', ' +0B101 ', '0o123', '-0xABC', '0x1a1',
    '12.5%', '1/2', '½', '3¼', 'π', 'Ⅻ', '1,000,000', '1 000', '- 001.20e+02', 
    'NaN', 'inf', '-Infinity']

for s in tests:
    print("%14s -> %-14s %-20s is_numeric: %-5s  str.isnumeric: %s" % (
        '"'+s+'"', numeric(s), type(numeric(s)), is_numeric(s), s.isnumeric() ))

Output:

           "0" -> 0              <class 'int'>        is_numeric: True   str.isnumeric: True
          "0." -> 0.0            <class 'float'>      is_numeric: True   str.isnumeric: False
          "00" -> 0              <class 'int'>        is_numeric: True   str.isnumeric: True
         "123" -> 123            <class 'int'>        is_numeric: True   str.isnumeric: True
        "0123" -> 123            <class 'int'>        is_numeric: True   str.isnumeric: True
        "+123" -> 123            <class 'int'>        is_numeric: True   str.isnumeric: False
        "-123" -> -123           <class 'int'>        is_numeric: True   str.isnumeric: False
       "-123." -> -123.0         <class 'float'>      is_numeric: True   str.isnumeric: False
     "-123e-4" -> -0.0123        <class 'float'>      is_numeric: True   str.isnumeric: False
     "-.8E-04" -> -8e-05         <class 'float'>      is_numeric: True   str.isnumeric: False
       "0.123" -> 0.123          <class 'float'>      is_numeric: True   str.isnumeric: False
         "(5)" -> (5+0j)         <class 'complex'>    is_numeric: True   str.isnumeric: False
   "-123+4.5j" -> (-123+4.5j)    <class 'complex'>    is_numeric: True   str.isnumeric: False
      "0b0101" -> 5              <class 'int'>        is_numeric: True   str.isnumeric: False
    " +0B101 " -> 5              <class 'int'>        is_numeric: True   str.isnumeric: False
       "0o123" -> 83             <class 'int'>        is_numeric: True   str.isnumeric: False
      "-0xABC" -> -2748          <class 'int'>        is_numeric: True   str.isnumeric: False
       "0x1a1" -> 417            <class 'int'>        is_numeric: True   str.isnumeric: False
       "12.5%" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
         "1/2" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
           "½" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: True
          "3¼" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: True
           "π" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
           "Ⅻ" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: True
   "1,000,000" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
       "1 000" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
"- 001.20e+02" -> None           <class 'NoneType'>   is_numeric: False  str.isnumeric: False
         "NaN" -> nan            <class 'float'>      is_numeric: True   str.isnumeric: False
         "inf" -> inf            <class 'float'>      is_numeric: True   str.isnumeric: False
   "-Infinity" -> -inf           <class 'float'>      is_numeric: True   str.isnumeric: False

Python: Regular expressions

import re
numeric = re.compile('[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?')
is_numeric = lambda x: numeric.fullmatch(x) != None

is_numeric('123.0')

Quackery

  [ char . over find 
    tuck over found iff
      [ swap pluck drop ]
    else nip ]                  is -point  ( $ --> $ )
   
  [ -point $->n nip ]           is numeric ( $ --> b )
         
  [ dup echo$ say " is" 
    numeric not if say " not"
    say " a valid number." cr ] is task    ( $ -->   )
   
  $ "152"        task
  $ "-3.1415926" task
  $ "Foo123"     task

Output:

152 is a valid number.
-3.1415926 is a valid number.
Foo123 is not a valid number.

R

> strings <- c("152", "-3.1415926", "Foo123")
> suppressWarnings(!is.na(as.numeric(strings)))
[1]  TRUE  TRUE FALSE

Racket

(define (string-numeric? s) (number? (string->number s)))

Or, since all non-#f are true:

(define string-numeric? string->number)

Raku

(formerly Perl 6)

Works with: Rakudo version 2017.11

Raku tries very hard to DWIM (do what I mean). As part of that, numeric strings are by default stored as allomorphic types which can be used as numbers or strings without any conversion. If we truly want to operate on strings, we have to explicitly coerce the allomorphs to strings. A subtlety that may not be immediately apparent, whitespace, empty strings and null strings may be treated as (False) boolean values in Raku, however booleans are allomorphic to numeric, so empty strings will coerce to a numeric value (0), and return as numeric unless specifically checked for. Interestingly, the actual strings 'True' and 'False' don't evaluate as numeric. (because there are no String | Boolean allomorphs.)

Note: These routines are usable for most cases but won't detect unicode non-digit numeric forms; E.G. vulgar fractions, Roman numerals, circled numbers, etc. If it is necessary to detect those as numeric, a full fledged grammar may be necessary.

sub is-number-w-ws( Str $term --> Bool ) { # treat Falsey strings as numeric
    $term.Numeric !~~ Failure;
}

sub is-number-wo-ws( Str $term --> Bool ) { # treat Falsey strings as non-numeric
    ?($term ~~ / \S /) && $term.Numeric !~~ Failure;
}

say "               Coerce     Don't coerce";
say '    String   whitespace    whitespace';
printf "%10s  %8s  %11s\n",
"<$_>", .&is-number-w-ws, .&is-number-wo-ws for
(|<1 1.2 1.2.3 -6 1/2 12e B17 1.3e+12 1.3e12 -2.6e-3 zero 0x 0xA10 0b1001 0o16 
0o18 2+5i True False Inf NaN 0x10.50 0b102 0o_5_3 ௫௯>, '  12  ', '1 1 1', '', ' ' ).map: *.Str;

               Coerce     Don't coerce
    String   whitespace    whitespace
       <1>      True         True
     <1.2>      True         True
   <1.2.3>     False        False
      <-6>      True         True
     <1/2>      True         True
     <12e>     False        False
     <B17>     False        False
 <1.3e+12>      True         True
  <1.3e12>      True         True
 <-2.6e-3>      True         True
    <zero>     False        False
      <0x>     False        False
   <0xA10>      True         True
  <0b1001>      True         True
    <0o16>      True         True
    <0o18>     False        False
    <2+5i>      True         True
    <True>     False        False
   <False>     False        False
     <Inf>      True         True
     <NaN>      True         True
 <0x10.50>      True         True
   <0b102>     False        False
  <0o_5_3>      True         True
      <௫௯>      True         True
 <   12  >      True         True
   <1 1 1>     False        False
        <>      True        False
       < >      True        False

RapidQ

isnumeric 
$Typecheck on

Defint FALSE, TRUE

FALSE = 0
TRUE = NOT FALSE

Function isNumeric(s as string, optchar as string) as integer
    If len(s) = 0 then
        Result = FALSE
        Exit Function
    End If
    if instr(s,"+") > 1 then
        Result = FALSE
        exit function
    end if    
    if instr(s,"-") > 1 then
        Result = FALSE
        exit function
    end if              
    Defint i, ndex = 0    
    For i = 1 to len(s)
        select case asc(mid$(s,i,1))
        case 43   '+
        case 45   '- 
        case 46 '.
            if ndex = 1 then
                Result = FALSE
                Exit function
            end if
            ndex = 1
        case 48 to 57  '0 to 9
        case else
            if instr(optchar,(mid$(s,i,1))) = 0 then 
                Result = FALSE
                exit function
            end if
        end select
    next
    Result = TRUE
End Function  

'============================================================
'Begin
'============================================================

showmessage (str$(isNumeric("-152.34","")))
end

REBOL

REBOL [
	Title: "Is Numeric?"
	URL: http://rosettacode.org/wiki/IsNumeric
]

; Built-in.

numeric?: func [x][not error? try [to-decimal x]]

; Parse dialect for numbers.

sign:   [0 1 "-"]
digit:  charset "0123456789"
int:    [some digit]
float:  [int "." int]
number: [
	sign float ["e" | "E"] sign int |
	sign int ["e" | "E"] sign int |
	sign float |
	sign int 
]

pnumeric?: func [x][parse x number]

; Test cases.

cases: parse {
   10 -99 
   10.43 -12.04 
   1e99 1.0e10 -10e3 -9.12e7 2e-4 -3.4E-5
   3phase  Garkenhammer  e  n3v3r  phase3
} none
foreach x cases [print [x  numeric? x  pnumeric? x]]

Retro

Retro does not have floating point numbers as part of the core system. For others, this can be done with:

'123 a:from-string TRUE [ swap c:digit? and ] a:reduce

REXX

/*REXX program determines if a string is numeric,  using REXX's rules for numbers.      */
yyy=' -123.78'                                   /*or some such.                        */

                                                 /*strings below are all numeric (REXX).*/
zzz= ' -123.78 '
zzz= '-123.78'
zzz= '2'
zzz= "2"
zzz= 2
zzz= '000000000004'
zzz= '+5'
zzz=  +5
zzz= ' +6 '
zzz= ' + 7 '
zzz= ' - 8 '
zzz= ' - .9'
zzz= '- 19.'
zzz= '.7'
zzz=  .7
zzz= '2e3'
zzz= 47e567
zzz= '2e-3'
zzz= '1.2e1'
zzz= ' .2E6'
zzz= ' 2.e5 '
zzz= '       +1.2E0002 '
zzz= '       +1.2e+002 '
zzz= ' +0000001.200e+002 '
zzz= ' - 000001.200e+002 '
zzz= ' - 000008.201e-00000000000000002 '

                     /*Note:  some REXX interpreters allow use of tab chars as blanks.  */

                     /*all statements below are equivalent.*/

if \datatype(yyy, 'n')        then say 'oops, not numeric:'  yyy
if \datatype(yyy, 'N')        then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'N')        then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'numeric')  then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'nimrod.')  then say 'oops, not numeric:'  yyy
if  datatype(yyy) \== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) /== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) ¬== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) ¬=  'NUM'   then say 'oops, not numeric:'  yyy

                /*note:  REXX only looks at the first char for DATATYPE's  2nd argument.*/

                /*note:  some REXX interpreters don't support the  ¬  (not)  character. */

Ring

see isdigit("0123456789") + nl +        # print 1
    isdigit("0123a")                    # print 0

RPL

This one-liner returns 1 if the string is either a real number, a complex number or a binary integer - and zero otherwise.

≪ IFERR STR→ THEN DROP 0 ELSE TYPE { 0 1 10 } SWAP POS SIGN END ≫ ‘NUM?’ STO

Ruby

def is_numeric?(s)
  begin
    Float(s)
  rescue
    false # not numeric
  else
    true # numeric
  end
end

or more compact:

def is_numeric?(s)
    !!Float(s) rescue false
end

NB! Since Ruby 2.6 you no longer need `rescue`:

def is_numeric?(s)
    !!Float(s, exception: false)
end

Adding `exception: false` will make it return `nil` instead.

sample

strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e)
strings.each do |str|
  puts "%9p => %s" % [str, is_numeric?(str)]
end

Output:

      "0" => true
    "0.0" => true
   "-123" => true
    "abc" => false
   "0x10" => true
  "0xABC" => true
   "123a" => false
 "-123e3" => true
 "0.1E-5" => true
    "50e" => false

Run BASIC

print isNumeric("123") 
print isNumeric("1ab")

' ------------------------
' Numeric Check
' 0 = bad
' 1 = good
' ------------------------
FUNCTION isNumeric(f$)
isNumeric = 1
f$	= trim$(f$)
if left$(f$,1) = "-" or left$(f$,1) = "+" then f$ = mid$(f$,2)
for i = 1 to len(f$)
        d$ = mid$(f$,i,1)
	if d$ = "," then goto [nxtDigit]
	if d$ = "." then
                if dot$ = "." then isNumeric = 0
		dot$	= "."
		goto [nxtDigit]
	end if
       if (d$ < "0") or (d$ > "9") then isNumeric = 0	
[nxtDigit]
next i
END FUNCTION

123 1
1ab 0

Rust

// This function is not limited to just numeric types but rather anything that implements the FromStr trait.
fn parsable<T: FromStr>(s: &str) -> bool {
    s.parse::<T>().is_ok()
}

Scala

import scala.util.control.Exception.allCatch

def isNumber(s: String): Boolean = (allCatch opt s.toDouble).isDefined

def isNumeric(input: String): Boolean = input.forall(_.isDigit)

Or a more complete version, using a complex regular expression:

def isNumeric2(str: String): Boolean = {
  str.matches(s"""[+-]?((\d+(e\d+)?[lL]?)|(((\d+(\.\d*)?)|(\.\d+))(e\d+)?[fF]?))""")
}

Or using the built-in number parsing and catching exceptions:

def isNumeric(str: String): Boolean = {
  !throwsNumberFormatException(str.toLong) || !throwsNumberFormatException(str.toDouble)
}
  
def throwsNumberFormatException(f: => Any): Boolean = {
  try { f; false } catch { case e: NumberFormatException => true }
}

Scheme

string->number returns #f when the string is not numeric and otherwise the number, which is non-#f and therefore true.

(define (numeric? s) (string->number s))

Seed7

The function isNumeric uses the function getNumber from the library scanstri.s7i. GetNumber reads a numeric literal from a string. The numeric literal is removed from the input string.

$ include "seed7_05.s7i";
  include "scanstri.s7i";

const func boolean: isNumeric (in var string: stri) is func
  result
    var boolean: isNumeric is FALSE;
  local
    var string: numberStri is "";
  begin
    numberStri := getNumber(stri);
    isNumeric := stri = "";
  end func;

Sidef

There is the the String.looks_like_number method, which returns true when a given strings looks like a number:

say "0.1E-5".looks_like_number;       #=> true

Alternatively, we can use regular expressions to determine this:

func is_numeric(s) {
    (s ~~ /^[+-]?+(?=\.?[0-9])[0-9_]*+(?:\.[0-9_]++)?(?:[Ee](?:[+-]?+[0-9_]+))?\z/) ||
    (s ~~ /^0(?:b[10_]*|x[0-9A-Fa-f_]*|[0-9_]+\b)\z/)
}

Sample:

var strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e);
for str in strings {
    say ("%9s => %s" % (str, is_numeric(str)))
}

Output:

        0 => true
      0.0 => true
     -123 => true
      abc => false
     0x10 => true
    0xABC => true
     123a => false
   -123e3 => true
   0.1E-5 => true
      50e => false

Simula

Simula uses the '&' instead of 'e' or 'E' for the exponent part of a floating point decimal number.

BEGIN

    BOOLEAN PROCEDURE ISNUMERIC(W); TEXT W;
    BEGIN
        BOOLEAN PROCEDURE MORE;
            MORE := W.MORE;
        CHARACTER PROCEDURE NEXT;
            NEXT := IF MORE THEN W.GETCHAR ELSE CHAR(0);
        CHARACTER PROCEDURE LAST;
            LAST := IF W.LENGTH = 0
                    THEN CHAR(0)
                    ELSE W.SUB(W.LENGTH,1).GETCHAR;
        CHARACTER CH;
        W.SETPOS(1);
        IF MORE THEN
        BEGIN
            CH := NEXT;
            IF CH = '-' OR CH = '+' THEN CH := NEXT;
            WHILE DIGIT(CH) DO CH := NEXT;
            IF CH = '.' THEN
            BEGIN
                CH := NEXT;
                IF NOT DIGIT(CH) THEN GOTO L;
                WHILE DIGIT(CH) DO CH := NEXT;
            END;
            IF CH = '&' THEN
            BEGIN
                CH := NEXT;
                IF CH = '-' OR CH = '+' THEN CH := NEXT;
                WHILE DIGIT(CH) DO CH := NEXT;
            END;
        END;
    L:  ISNUMERIC := (W.LENGTH > 0) AND THEN (NOT MORE) AND THEN DIGIT(LAST);
    END;

    REAL X;
    TEXT T;
    FOR X := 0, -3.1415, 2.768&+31, 5&10, .5, 5.&10 DO
    BEGIN
        OUTREAL(X, 10, 20);
        OUTIMAGE;
    END;

    OUTIMAGE;

    FOR T :- "0", "-3.1415", "2.768&+31", ".5", "5&22" DO
    BEGIN
        OUTTEXT(IF ISNUMERIC(T) THEN "    NUMERIC " ELSE "NOT NUMERIC ");
        OUTCHAR('"');
        OUTTEXT(T);
        OUTCHAR('"');
        IF T = "0" THEN OUTCHAR(CHAR(9)); OUTCHAR(CHAR(9));
        COMMENT PROBE ;
        X := T.GETREAL;
        OUTREAL(X, 10, 20);
        OUTIMAGE;
    END;

    OUTIMAGE;

    X := 5.&10;
   !X := 5&;
   !X := 5.;
    X := .5;
    FOR T :- "", "5.", "5&", "5&+", "5.&", "5.&-", "5.&10" DO
    BEGIN
        OUTTEXT(IF ISNUMERIC(T) THEN "    NUMERIC " ELSE "NOT NUMERIC ");
        OUTCHAR('"');
        OUTTEXT(T);
        OUTCHAR('"');
        OUTIMAGE;
    END;

END

Output:

    0.000000000&+000
   -3.141500000&+000
    2.768000000&+031
    5.000000000&+010
    5.000000000&-001
    5.100000000&+000

    NUMERIC "0"             0.000000000&+000
    NUMERIC "-3.1415"      -3.141500000&+000
    NUMERIC "2.768&+31"     2.768000000&+031
    NUMERIC ".5"            5.000000000&-001
    NUMERIC "5&22"          5.000000000&+022

NOT NUMERIC ""
NOT NUMERIC "5."
NOT NUMERIC "5&"
NOT NUMERIC "5&+"
NOT NUMERIC "5.&"
NOT NUMERIC "5.&-"
NOT NUMERIC "5.&10"

Smalltalk

Works with: GNU Smalltalk

The String class has the method isNumeric; this method (at least on version 3.0.4) does not recognize as number strings like '-123'! So I've written an extension...

String extend [
  realIsNumeric [
     (self first = $+) |
     (self first = $-) 
        ifTrue: [
           ^ (self allButFirst) isNumeric
        ]
        ifFalse: [
           ^ self isNumeric
        ]
  ]
]

{ '1234'.            "true"
  '3.14'. '+3.8111'. "true"
  '+45'.             "true"
  '-3.78'.           "true"
  '-3.78.23'. "false"
  '123e3'     "false: the notation is not recognized"
} do: [ :a | a realIsNumeric printNl ]

Works with: Smalltalk/X

Works with: GNU Smalltalk

(should work with all)

(Number readFrom:(aString readStream) onError:[nil]) notNil

to handle radix numbers (such as 2r10111), use:

(Scanner scanNumberFrom:(aString readStream)) notNil

SNOBOL4

This task is easy in Snobol. Use the convert( ) function as a predicate returning success (T) or failure (F) for string to real conversion.

        define('nchk(str)') :(nchk_end)
nchk    convert(str,'real') :s(return)f(freturn)
nchk_end        

*       # Wrapper for testing
        define('isnum(str)') :(isnum_end)
isnum   isnum = 'F'; isnum = nchk(str) 'T'
        isnum = isnum ': ' str :(return)
isnum_end        

*       # Test and display
        output = isnum('123')
        output = isnum('123.0')
        output = isnum('123.')
        output = isnum('-123')
        output = isnum('3.14159')
        output = isnum('1.2.3')
        output = isnum('abc')
        output = isnum('A440')
end

Output:

T: 123
T: 123.0
T: 123.
T: -123
T: 3.14159
F: 1.2.3
F: abc
F: A440

SQL

Works with: MS SQL version Server 2005

declare @s varchar(10)
set @s = '1234.56'

print isnumeric(@s) --prints 1 if numeric, 0 if not.

if isnumeric(@s)=1 begin print 'Numeric' end 
else print 'Non-numeric'

SQL PL

Works with: Db2 LUW

version 9.7 or higher.

With SQL PL:

--#SET TERMINATOR @

CREATE OR REPLACE FUNCTION IS_NUMERIC (
  IN STRING VARCHAR(10)
 ) RETURNS SMALLINT
 -- ) RETURNS BOOLEAN
 BEGIN
  DECLARE RET SMALLINT;
  -- DECLARE RET BOOLEAN;
  DECLARE TMP INTEGER;
  DECLARE CONTINUE HANDLER FOR SQLSTATE '22018'
    SET RET = 1;
    -- SET RET = FALSE;

  SET RET = 0;
  --SET RET = TRUE;
  SET TMP = INTEGER(STRING);
  RETURN RET;
 END @

VALUES IS_NUMERIC('5')@
VALUES IS_NUMERIC('0')@
VALUES IS_NUMERIC('-1')@
VALUES IS_NUMERIC('A')@
VALUES IS_NUMERIC('-')@
VALUES IS_NUMERIC('z')@
VALUES IS_NUMERIC('')@
VALUES IS_NUMERIC(' ')@

Output:

db2 -td@
db2 => BEGIN
...
db2 (cont.) => END @
DB20000I  The SQL command completed successfully.

VALUES IS_NUMERIC('5')

1     
------
     0

  1 record(s) selected.


VALUES IS_NUMERIC('0')

1     
------
     0

  1 record(s) selected.


VALUES IS_NUMERIC('-1')

1     
------
     0

  1 record(s) selected.


VALUES IS_NUMERIC('A')

1     
------
     1

  1 record(s) selected.


VALUES IS_NUMERIC('-')

1     
------
     1

  1 record(s) selected.


VALUES IS_NUMERIC('z')

1     
------
     1

  1 record(s) selected.


VALUES IS_NUMERIC('')

1     
------
     1

  1 record(s) selected.


VALUES IS_NUMERIC(' ')

1     
------
     1

  1 record(s) selected.

Standard ML

(* this function only recognizes integers in decimal format *)
fun isInteger s = case Int.scan StringCvt.DEC Substring.getc (Substring.full s) of
   SOME (_,subs) => Substring.isEmpty subs
 | NONE          => false

fun isReal s = case Real.scan Substring.getc (Substring.full s) of
   SOME (_,subs) => Substring.isEmpty subs
 | NONE          => false

fun isNumeric s = isInteger s orelse isReal s

Swift

Works with: Swift version 2.x+

func isNumeric(a: String) -> Bool {
  return Double(a) != nil
}

Works with: Swift version 1.x

This one only checks whether it is an integer:

func isNumeric(a: String) -> Bool {
  return a.toInt() != nil
}

Tcl

proc isNumeric str {string is double -strict $str}

TMG

Unix TMG dialect. NOTE: the program also performs some basic normalization (namely, removing the plus sign and translating "E" to "e"):

prog:   ignore(<< >>)
        parse(line)\prog
        parse(error)\prog;
line:   number *;
number: ignore(none)
        sign float (exp | ={})
        = { < True: > 3 2 1 * };
sign:   <+>={} | <->={<->} | ={};
float:  int ( <.> decim = { 2 <.> 1 } | = { 1 } )
     |  <.> int = { <.> 1 };
int:    smark any(digit) string(digit) scopy;
decim:  smark string(digit) scopy;
exp:    any(<<eE>>) sign int = { <e> 2 1 };

error:  smark any(nonl) ignore(none) string(nonl) scopy * = { <False: > 1 * };

digit:  <<0123456789>>;
none:   <<>>;
nonl:   !<<
>>;

Sample input:

123
+12345.678
.678
1.
+1.0E+99
-7.
-123e-123
00000
.
1.2.3
0x123
a1-a5
1 000 000
1,000,000
1.00e1e1

Sample output:

 True: 123
 True: 12345.678
 True: .678
 True: 1.
 True: 1.0e99
 True: -7.
 True: -123e-123
 True: 00000
False: .
False: 1.2.3
False: 0x123
False: a1-a5
False: 1 000 000
False: 1,000,000
False: 1.00e1e1

Toka

Returns a flag of TRUE if character-string parameter represents a signed or unsigned integer. Otherwise returns a flag of FALSE. The success or failure is dependent on the source is valid in the current numeric base. The >number function also recognizes several optional prefixes for overriding the current base during conversion.

[ ( string -- flag )
  >number nip ] is isNumeric

( Some tests )
decimal
" 100" isNumeric .     ( succeeds, 100 is a valid decimal integer )
" 100.21" isNumeric .  ( fails, 100.21 is not an integer)
" a" isNumeric .       ( fails, 'a' is not a valid integer in the decimal base )
" $a" isNumeric .      ( succeeds, because $ is a valid override prefix )
                       ( denoting that the following character is a hexadecimal number )

True BASIC

Translation of: RapidQ

DECLARE FUNCTION isnumeric$

LET true$ = "True"
LET false$ = "False"
LET s$ = "-152.34"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "1234.056789"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "1234.56"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "021101"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "Dog"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "Bad125"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "-0177"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "+123abcd.ef"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "54321"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "123xyz"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "xyz"
PRINT s$, " => "; isnumeric$(s$)
FUNCTION isnumeric$(s$)
    LET optchar$ = ""
    IF len(s$) = 0 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    IF pos(s$,"+") > 1 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    IF pos(s$,"-") > 1 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    LET ndex = 0
    FOR i = 1 to len(s$)
        SELECT CASE ord((s$)[i:i+1-1][1:1])
        CASE 43                   !+
        CASE 45                   !-
        CASE 46                   !.
             IF ndex = 1 then
                LET isnumeric$ = false$
                EXIT FUNCTION
             END IF
             LET ndex = 1
        CASE 48 to 57             !0 a 9
        CASE else
             IF pos(optchar$,((s$)[i:i+1-1])) = 0 then
                LET isnumeric$ = false$
                EXIT FUNCTION
             END IF
        END SELECT
    NEXT i
    LET isnumeric$ = true$
END FUNCTION
END

UNIX Shell

#!/bin/bash
isnum() {
  printf "%f" $1 >/dev/null 2>&1
}


check() {
  if isnum $1
  then
     echo "$1 is numeric"
  else
     echo "$1 is NOT numeric"
  fi
}

check 2
check -3
check +45.44
check -33.332
check 33.aa
check 3.3.3

Output:

2 is numeric
-3 is numeric
+45.44 is numeric
-33.332 is numeric
33.aa is NOT numeric
3.3.3 is NOT numeric

Ursa

def isnum (string str)
	try
		double str
		return true
	catch valueerror
		return false
	end try
end isnum

VBA

In France, IsNumeric("123.45") return False. So we have to check the "." or "," and replace it by the Application.DecimalSeparator.

Sub Main()
    Debug.Print Is_Numeric("")
    Debug.Print Is_Numeric("-5.32")
    Debug.Print Is_Numeric("-51,321 32")
    Debug.Print Is_Numeric("123.4")
    Debug.Print Is_Numeric("123,4")
    Debug.Print Is_Numeric("123;4")
    Debug.Print Is_Numeric("123.4x")
End Sub

Private Function Is_Numeric(s As String) As Boolean
Dim Separat As String, Other As String
    Separat = Application.DecimalSeparator
    Other = IIf(Separat = ",", ".", ",")
    Is_Numeric = IsNumeric(Replace(s, Other, Separat))
End Function

VBScript

IsNumeric(Expr)

Returns a True if numeric and a false if not.

Vedit macro language

This routine returns TRUE if there is numeric value at current cursor location. Only signed and unsigned integers are recognized, in decimal, hex (preceded with 0x) or octal (preceded with 0o). Remove the SUPPRESS option to evaluate an expression instead of single numeric value.

:IS_NUMERIC:
if (Num_Eval(SUPPRESS)==0 && Cur_Char != '0') {
    Return(FALSE)
} else {
    Return(TRUE)
}

Visual Basic .NET

Works with: Visual Basic .NET version 2005

Dim Value As String = "+123"

If IsNumeric(Value) Then
    PRINT "It is numeric."
End If

V (Vlang)

import strconv

fn is_numeric(s string) bool {
	strconv.atof64(s) or {
		return false
	}
	return true
}

fn main() {
    println("Are these strings numeric?")
    strings := ["1", "3.14", "-100", "1e2", "NaN", "rose", "0xff", "0b110"]
    for s in strings {
        println("  ${s:4} -> ${is_numeric(s)}")
    }
}

Output:

Are these strings numeric?
     1 -> true
  3.14 -> true
  -100 -> true
   1e2 -> true
   NaN -> false
  rose -> false
  0xff -> true
  0b110 -> true

Wren

Library: Wren-fmt

Wren's Num class already has a static method which does what this task requires.

import "./fmt" for Fmt

System.print("Are these strings numeric?")

for (s in ["1", "3.14", "-100", "1e2", "NaN", "0xaf", "rose"]) {
    var  i = Num.fromString(s) // returns null if 's' is not numeric
    System.print("  %(Fmt.s(4, s)) -> %((i != null) ? "yes" : "no")")
}

Output:

Are these strings numeric?
     1 -> yes
  3.14 -> yes
  -100 -> yes
   1e2 -> yes
   NaN -> yes
  0xaf -> yes
  rose -> no

XLISP

The inbuilt function STRING->NUMBER returns the numeric value of a string if it can. We discard this value and return the Boolean value 'true'; otherwise, the IF conditional will not be satisfied and will return 'false'.

(DEFUN NUMERICP (X)
    (IF (STRING->NUMBER X) T))

XPL0

The compiler is more strict in the characters it accepts as numeric than what is accepted here. This program indicates more of what the input intrinsics (IntIn, RlIn and HexIn) would accept as numeric.

string 0;

func IsNumeric(Str);
char Str;
[while Str(0) # 0 do
    [if Str(0) >= ^0 and Str(0) <= ^9 then return true;
    if Str(0) = ^$ then
        [if Str(1) >= ^0 and Str(1) <= ^9 then return true;
         if Str(1) >= ^A and Str(1) <= ^F then return true;
         if Str(1) >= ^a and Str(1) <= ^f then return true;
        ];
    Str:= Str+1;
    ];
return false;
];

int Strs, S;
[Text(0, "Are these strings numeric?^m^j");
Strs:= ["1", "3.14", "-100", "1e2", "NaN", "$af", "%1_1011", "rose", ". 3", "num9", "x$ 9", "x$ a"];
for S:= 0 to 12-1 do
    [Text(0, if IsNumeric(Strs(S)) then "yes : " else "no  : ");
    Text(0, Strs(S));
    CrLf(0);
    ];
]

Output:

Are these strings numeric?
yes : 1
yes : 3.14
yes : -100
yes : 1e2
no  : NaN
yes : $af
yes : %1_1011
no  : rose
yes : . 3
yes : num9
yes : x$ 9
no  : x$ a

Z80 Assembly

Works with: CP/M 3.1 version YAZE-AG-2.51.2 Z80 emulator

Works with: ZSM4 macro assembler version YAZE-AG-2.51.2 Z80 emulator

Use the /S8 switch on the ZSM4 assembler for 8 significant characters for labels and names

	;
	; Check if input string is a number using Z80 assembly language
	;
	; Runs under CP/M 3.1 on YAZE-AG-2.51.2 Z80 emulator
	; Assembled with zsm4 on same emulator/OS, uses macro capabilities of said assembler
	; Created with vim under Windows
	;
	; 2023-04-04 Xorph
	;

	;
	; Useful definitions
	;

	bdos	equ 05h		; Call to CP/M BDOS function
	strdel	equ 6eh		; Set string delimiter
	readstr	equ 0ah		; Read string from console
	wrtstr	equ 09h		; Write string to console

	nul	equ 00h		; ASCII control characters
	esc	equ 1bh
	cr	equ 0dh
	lf	equ 0ah

	cnull	equ '0'		; ASCII character constants
	cnine	equ '9'
	cminus	equ '-'
	cdot	equ '.'

	buflen	equ 30h		; Length of input buffer
	minbit	equ 00h		; Bit 0 is used as flag for '-'
	dotbit	equ 01h		; Bit 1 is used as flag for '.'

	;
	; Macros for BDOS calls
	;

setdel 	macro	char		; Set string delimiter to char
	ld	c,strdel
	ld	e,char
	call	bdos
	endm

print 	macro	msg		; Output string to console
	ld	c,wrtstr
	ld	de,msg
	call	bdos
	endm

newline	macro			; Print newline
	ld	c,wrtstr
	ld	de,crlf
	call	bdos
	endm

readln 	macro	buf		; Read a line from input
	ld	c,readstr
	ld	de,buf
	call	bdos
	endm

	;
	; =====================
	; Start of main program
	; =====================
	;

	cseg

isnum:
	setdel	nul		; Set string terminator to nul ('\0') - '$' is default in CP/M
	print	help
	newline
	newline

readnum:
	ld	b,buflen	; Clear input buffer
	ld	hl,bufcont
clrloop:
	ld	(hl),0
	inc	hl
	djnz	clrloop

	readln	inputbuf	; Read a line from input
	newline			; Newline is discarded during input, so write one...

	ld	a,(inputbuf+1)	; Length of actual input
	cp	0		; If empty input, quit
	ret	z

	ld	b,a		; Loop counter for djnz instruction
	ld	c,0		; Use c for flags: '-' and '.' may be encountered at most once, '-' only at start
	ld	hl,bufcont	; Start of actual input

loop:
	ld	a,(hl)		; Get next character into a

	cp	cminus		; Check minus sign
	jr	z,chkminus

	cp	cdot		; Check dot
	jr	z,chkdot

	cp	cnull		; Check if below '0'
	jr	c,notanum

	cp	cnine+1		; Check if above '9'
	jr	nc,notanum

checknxt:
	set	minbit,c	; Whatever the case, no more '-' are allowed after the first character
	inc	hl		; Increase hl to next character and repeat until done
	djnz	loop

	print	bufcont		; If we made it this far, we are done and the string is numeric
	print	yesmsg
	newline
	newline

done:
	jp	readnum		; Read next input from user until terminated with ^C or empty input
	ret			; Return to CP/M (unreachable code)

notanum:
	print	bufcont		; Print failure message
	print	nomsg
	newline
	newline
	jr	done

chkminus:
	bit	minbit,c	; If a '-' is encountered and the flag is already set, the string is not numeric
	jr	nz,notanum
	set	minbit,c	; Otherwise, set flag and check next character
	jr	checknxt

chkdot:
	bit	dotbit,c	; If a '.' is encountered and the flag is already set, the string is not numeric
	jr	nz,notanum
	set	dotbit,c	; Otherwise, set flag and check next character
	jr	checknxt

	;
	; ===================
	; End of main program
	; ===================
	;

	;
	; ================
	; Data definitions
	; ================
	;

	dseg

help:
	defz	'Enter numbers to check, end with empty line or ^C'

inputbuf:			; Input buffer for CP/M BDOS call
	defb	buflen		; Maximum possible length
	defb	00h		; Returned length of actual input
bufcont:
	defs	buflen		; Actual input area
	defb	nul		; Null terminator for output, if buffer is filled completely

yesmsg:
	defz	' is numeric'
nomsg:
	defz	' is not numeric'

crlf:	defb	cr,lf,nul	; Generic newline

Output:

E>isnum
Enter numbers to check, end with empty line or ^C

1234
1234 is numeric

hello
hello is not numeric

12.34
12.34 is numeric

-98.76
-98.76 is numeric

4.6.76
4.6.76 is not numeric

34-56-23
34-56-23 is not numeric

-.9876543210
-.9876543210 is numeric

444555.
444555. is numeric

1234c
1234c is not numeric

123e45
123e45 is not numeric

zkl

fcn isNum(text){
   try{ text.toInt(); True }
   catch{ try{ text.toFloat(); True }
          catch{ False }
   }
}

isNum("123.4")  //-->True
isNum("123")    //-->True
isNum("-123.4") //-->True
isNum("123.4x") //-->False
isNum("hoho")   //-->False
isNum(123.4)    //-->True
isNum(123)      //-->True

Zoea

program: numeric 
  case: 1   input: '1'      output: true 
  case: 2   input: '-3'     output: true 
  case: 3   input: '22.7'   output: true 
  case: 4   input: 'a'      output: false 
  case: 5   input: 'Fred'   output: false 
  case: 6   input: ''       output: false

Zoea Visual

Determine if string is numeric