Determine if a string is numeric: Difference between revisions
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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. |
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. |
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{{Template:Strings}} |
{{Template:Strings}} |
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Revision as of 14:48, 7 June 2021
You are encouraged to solve this task according to the task description, using any language you may know.
- 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.
- Metrics
- Counting
- Word frequency
- Letter frequency
- Jewels and stones
- I before E except after C
- Bioinformatics/base count
- Count occurrences of a substring
- Count how many vowels and consonants occur in a string
- Remove/replace
- XXXX redacted
- Conjugate a Latin verb
- Remove vowels from a string
- String interpolation (included)
- Strip block comments
- Strip comments from a string
- Strip a set of characters from a string
- Strip whitespace from a string -- top and tail
- Strip control codes and extended characters from a string
- Anagrams/Derangements/shuffling
- Word wheel
- ABC problem
- Sattolo cycle
- Knuth shuffle
- Ordered words
- Superpermutation minimisation
- Textonyms (using a phone text pad)
- Anagrams
- Anagrams/Deranged anagrams
- Permutations/Derangements
- Find/Search/Determine
- ABC words
- Odd words
- Word ladder
- Semordnilap
- Word search
- Wordiff (game)
- String matching
- Tea cup rim text
- Alternade words
- Changeable words
- State name puzzle
- String comparison
- Unique characters
- Unique characters in each string
- Extract file extension
- Levenshtein distance
- Palindrome detection
- Common list elements
- Longest common suffix
- Longest common prefix
- Compare a list of strings
- Longest common substring
- Find common directory path
- Words from neighbour ones
- Change e letters to i in words
- Non-continuous subsequences
- Longest common subsequence
- Longest palindromic substrings
- Longest increasing subsequence
- Words containing "the" substring
- Sum of the digits of n is substring of n
- Determine if a string is numeric
- Determine if a string is collapsible
- Determine if a string is squeezable
- Determine if a string has all unique characters
- Determine if a string has all the same characters
- Longest substrings without repeating characters
- Find words which contains all the vowels
- Find words which contains most consonants
- Find words which contains more than 3 vowels
- Find words which first and last three letters are equals
- Find words which odd letters are consonants and even letters are vowels or vice_versa
- Formatting
- Substring
- Rep-string
- Word wrap
- String case
- Align columns
- Literals/String
- Repeat a string
- Brace expansion
- Brace expansion using ranges
- Reverse a string
- Phrase reversals
- Comma quibbling
- Special characters
- String concatenation
- Substring/Top and tail
- Commatizing numbers
- Reverse words in a string
- Suffixation of decimal numbers
- Long literals, with continuations
- Numerical and alphabetical suffixes
- Abbreviations, easy
- Abbreviations, simple
- Abbreviations, automatic
- Song lyrics/poems/Mad Libs/phrases
- Mad Libs
- Magic 8-ball
- 99 Bottles of Beer
- The Name Game (a song)
- The Old lady swallowed a fly
- The Twelve Days of Christmas
- Tokenize
- Text between
- Tokenize a string
- Word break problem
- Tokenize a string with escaping
- Split a character string based on change of character
- Sequences
8th
<lang Forth>: number? >n >kind ns:n n:= ;</lang>
AArch64 Assembly
<lang AArch64 Assembly> /* 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"
</lang>
ActionScript
<lang actionscript>public function isNumeric(num:String):Boolean {
return !isNaN(parseInt(num));
}</lang>
Ada
The first file is the package interface containing the declaration of the Is_Numeric function. <lang ada>package Numeric_Tests is
function Is_Numeric (Item : in String) return Boolean;
end Numeric_Tests;</lang> The second file is the package body containing the implementation of the Is_Numeric function. <lang ada>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;</lang> The last file shows how the Is_Numeric function can be called. <lang ada>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;</lang>
- Output:
152 results in TRUE -3.1415926 results in TRUE Foo123 results in FALSE
Aime
<lang 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;
}</lang>
ALGOL 68
<lang algol68>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
))
) </lang>
- Output:
152 results in T -3.1415926 results in T Foo123 results in F
ALGOL W
<lang algolw>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.</lang>
- 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. <lang Apex> 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 </lang>
APL
<lang apl> ⊃⎕VFI{w←⍵⋄((w='-')/w)←'¯'⋄w}'152 -3.1415926 Foo123'
1 1 0</lang> Works with more recent versions of Dyalog APL<lang 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</lang>
AppleScript
<lang 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</lang>
- Output:
<lang AppleScript>{false, false, false, true, true, true, true, false, false, false}</lang>
The classic way's slightly simpler, since the coercion result must be a real or an integer if the coercion itself didn't error.
<lang applescript>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</lang>
ARM Assembly
<lang ARM Assembly>
/* 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
</lang>
Arturo
<lang rebol>print numeric? "hello world" print numeric? "1234" print numeric? "1234 hello world" print numeric? "12.34" print numeric? "!#@$" print numeric? "-1.23"</lang>
- 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. <lang autohotkey>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</lang>
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: <lang AWK> $ awk 'function isnum(x){return(x==x+0)} BEGIN{print isnum("hello"),isnum("-42")}' </lang>
- Output:
0 1
BaCon
<lang 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</lang>
- 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
<lang qbasic>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</lang>
Commodore BASIC
<lang commodorebasic>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</lang>
- Output:
Enter a string? 15893 You entered a number. ready. run Enter a string? Llamas That is not a number. ready. █
QB64
<lang 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 </lang>
- 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$) in this case would have stopped after it converted the "99" portion of the input, which when converted back to a string and compared to the original input would not result in an equality. 9E4 the program reads as an exponential value.
Batch File
<lang dos>set /a a=%arg%+0 >nul if %a% == 0 ( if not "%arg%"=="0" ( echo Non Numeric. ) else ( echo Numeric. ) ) else ( echo Numeric. )</lang>
BBC BASIC
<lang bbcbasic> REPEAT
READ N$
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
</lang>
- 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
<lang 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">:#,_@^ <</lang>
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
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'.
<lang bracmat>43257349578692:/
F
260780243875083/35587980:/
S
247/30:~/#
F
80000000000:~/#
S</lang>
Bracmat doesn't do floating point computations (historical reason: the Acorn Risc Machine a.k.a. ARM processor in the Archimedes computer did not have an FPU), but the pattern ~/# (|"." (|? 0|`) (|~/#:>0)) (|(E|e) ~/#) recognises string representations of floating point numbers.
<lang bracmat>@("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</lang>
To do computations with such "floating point strings" you would have to convert such strings to fractional representations first. <lang bracmat>(float2fraction=
integerPart decimalPart d1 dn exp sign
. @( !arg
: ~/#?integerPart
( &0:?decimalPart:?d1:?dn
| "."
[?d1
(|? 0|`)
( &0:?decimalPart
| ~/#?decimalPart:>0
)
[?dn
)
( &0:?exp
| (E|e) ~/#?exp
)
)
& ( !integerPart*(-1:?sign):>0:?integerPart
| 1:?sign
)
& !sign*(!integerPart+!decimalPart*10^(!d1+-1*!dn))*10^!exp
);
( out$float2fraction$"1.2" & out$float2fraction$"1.02" & out$float2fraction$"1.01" & out$float2fraction$"10.01" & out$float2fraction$"10.01e10" & out$float2fraction$"10.01e1" & out$float2fraction$"10.01e2" & out$float2fraction$"10.01e-2" & out$float2fraction$"-10.01e-2" & out$float2fraction$"-10e-2" & out$float2fraction$"0.000" ); </lang>
- Output:
6/5 51/50 101/100 1001/100 100100000000 1001/10 1001 1001/10000 -1001/10000 -1/10 0
Burlesque
<lang burlesque> ps^^-]to{"Int""Double"}\/~[\/L[1==?* </lang>
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).
<lang c>#include <ctype.h>
- include <stdlib.h>
int isNumeric (const char * s) {
if (s == NULL || *s == '\0' || isspace(*s))
return 0;
char * p;
strtod (s, &p);
return *p == '\0';
}</lang>
C#
Framework: .NET 2.0+
<lang csharp>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
}</lang>
Framework: .NET 1.0+
<lang csharp>public static bool IsNumeric(string s) {
try
{
Double.Parse(s);
return true;
}
catch
{
return false;
}
}</lang>
C++
Using stringstream: <lang cpp>#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 ); } </lang>
Using find: <lang cpp> 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); } </lang>
Using all_of (requires C++11) <lang cpp> bool isNumeric(const std::string& input) {
return std::all_of(input.begin(), input.end(), ::isdigit);
} </lang>
CFScript
ColdFusion Script (CfScript) <lang cfm>isNumeric(42)</lang>
Clojure
<lang 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))))</lang>
This works with any sequence of characters, not just Strings, e.g.: <lang clojure>(numeric? [\1 \2 \3]) ;; yields logical true</lang>
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: <lang clojure> (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)))))))
</lang> <lang clojure> user=> (number-string? "2r101010") true user=> (number-string? "22/7") true </lang>
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.
<lang cobol> 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.</lang>
Implementation
<lang cobol> 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
.</lang>
CoffeeScript
The isFinite function is built into JavaScript, so we don't need to create our own function in CoffeeScript. <lang 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 </lang>
ColdFusion
Adobe's ColdFusion
<lang cfm><cfset TestValue=34>
TestValue: <cfoutput>#TestValue#</cfoutput>
<cfif isNumeric(TestValue)>
is Numeric.
<cfelse>
is NOT Numeric.
</cfif>
<cfset TestValue="NAS">
TestValue: <cfoutput>#TestValue#</cfoutput>
<cfif isNumeric(TestValue)>
is Numeric.
<cfelse>
is NOT Numeric.
</cfif></lang>
Alternative solution
<lang><cfoutput>#isNumeric(42)#</cfoutput></lang>
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. <lang lisp>(defun numeric-string-p (string)
(let ((*read-eval* nil)) (ignore-errors (numberp (read-from-string string)))))</lang>
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.
<lang lisp>(defun numeric-string-p (string)
(ignore-errors (parse-number:parse-number string))) ; parse failed, return false (nil)</lang>
D
Standard Version
Using the standard Phobos function (currently binary and hex literals are not recognized):
<lang d>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));
}</lang>
- 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
<lang d>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 .. $].to!ulong(2)
.collectException!ConvException;
else
return false;
}
return true;
}
void main() {
foreach (immutable s; ["12", " 12\t", "hello12", "-12", "02",
"0-12", "+12", "1.5", "1,000", "1_000",
"0x10", "0b10101111_11110000_11110000_00110011",
"-0b10101", "0x10.5"])
writefln(`isNumeric("%s"): %s`, s, s.isNumeric);
}</lang>
- Output:
isNumeric("12"): true
isNumeric(" 12 "): true
isNumeric("hello12"): false
isNumeric("-12"): true
isNumeric("02"): true
isNumeric("0-12"): false
isNumeric("+12"): true
isNumeric("1.5"): true
isNumeric("1,000"): true
isNumeric("1_000"): true
isNumeric("0x10"): true
isNumeric("0b10101111_11110000_11110000_00110011"): true
isNumeric("-0b10101"): false
isNumeric("0x10.5"): false
Delphi
This simple function is a wrapper around a built-in Delphi function
<lang Delphi> function IsNumericString(const inStr: string): Boolean; var
i: extended;
begin
Result := TryStrToFloat(inStr,i);
end; </lang>
This console application tests the function:
<lang Delphi> program isNumeric;
{$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.
</lang>
- Output:
Example summarised
123 is numeric -123.456 is numeric -123.-456 is NOT numeric .345 is numeric m1k3 is NOT numeric
Dyalect
<lang dyalect>func String.isNumeric() {
try {
parse(this) is Integer or Float
} catch _ {
false
}
}
var str = "1234567" print(str.isNumeric())</lang>
Déjà Vu
<lang dejavu>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 )</lang>
- Output:
"-3" true "12ef" false "12e3" true "hello" false "3.14" true "0" true "1" true
E
<lang e>def isNumeric(specimen :String) {
try {
<import:java.lang.makeDouble>.valueOf(specimen)
return true
} catch _ {
return false
}
}</lang>
EasyLang
<lang>func is_numeric a$ . r .
h = number a$ r = 1 - error # because every variable must be used h = h
. test$[] = [ "abc" "21a" "1234" "-13" "7.65" ] for i range len test$[]
call is_numeric test$[i] r if r = 1 print test$[i] & " is numeric" else print test$[i] & " is not numeric" .
.</lang>
EchoLisp
The conversion function string->number returns #f - false - in the string is not a number, else returns a number, which is #t - true - as far as logical operations are concerned <lang scheme> (string->number "albert")
→ #f
(string->number -666)
→ -666
(if (string->number 666) 'YES 'NO)
→ YES
</lang>
Elixir
<lang elixir>defmodule RC do
def is_numeric(str) do
case Float.parse(str) do
{_num, ""} -> true
_ -> false
end
end
end
["123", "-12.3", "123.", ".05", "-12e5", "+123", " 123", "abc", "123a", "12.3e", "1 2"] |> Enum.filter(&RC.is_numeric/1)</lang>
- Output:
["123", "-12.3", "-12e5", "+123"]
Erlang
Erlang doesn't come with a way to say if a string represents a numeric value or not, but does come with the built-in function is_number/1, which will return true if the argument passed is either an integer or a float. Erlang also has two functions to transform a string to either a floating number or an integer, which will be used in conjunction with is_number/1.
<lang erlang>is_numeric(L) ->
Float = (catch erlang:list_to_float(L)), Int = (catch erlang:list_to_integer(L)), is_number(Float) orelse is_number(Int).</lang>
ERRE
Short form using predeclared ERRE functions VAL and STR$. <lang erre> 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 </lang>
- Output:
Enter a string? 12.30 is num
Euphoria
<lang 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</lang>
F#
<lang fsharp>let is_numeric a = fst (System.Double.TryParse a)</lang>
Factor
<lang factor>: numeric? ( string -- ? ) string>number >boolean ;</lang>
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.
<lang fantom> 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"))
}
} </lang>
- Output:
For '2': true For '-2': true For '2.5': true For '2a5': false For '-2.1e5': true
Forth
<lang forth>: 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 )</lang>
Fortran
<lang 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</lang>
Free Pascal
<lang 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;</lang>
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.
<lang freebasic>' 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</lang>
- 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
Gambas
<lang 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</lang> Output:
'Charlie' is a string '-00.256666' is numeric
Go
This uses a library function to meet the task's requirements: <lang go>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))
}
}</lang>
- 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: <lang go>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))
}</lang>
- 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. <lang groovy>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()
}</lang>
Test Program: <lang groovy>println isNumeric('1') println isNumeric('-.555') println isNumeric('1,000,000') println isNumeric(' 1 1 1 1 ') println isNumeric('abcdef')</lang>
- 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):
<lang haskell>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</lang>
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:
<lang haskell>areDigits = all isDigit isDigit selects ASCII digits i.e. '0'..'9' isOctDigit selects '0'..'7' isHexDigit selects '0'..'9','A'..'F','a'..'f'</lang>
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. <lang ActionScript> 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; } } </lang>
HicEst
<lang 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</lang>
i
<lang 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") }</lang>
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. <lang Icon> write(image(x), if numeric(x) then " is numeric." else " is not numeric") </lang>
IDL
<lang idl>function isnumeric,input
on_ioerror, false test = double(input) return, 1 false: return, 0
end</lang>
Could be called like this:
<lang idl>if isnumeric('-123.45e-2') then print, 'yes' else print, 'no'
- ==> yes
if isnumeric('picklejuice') then print, 'yes' else print, 'no'
- ==> no</lang>
J
<lang j>isNumeric=: _ ~: _ ". ] isNumericScalar=: 1 -: isNumeric TXT=: ,&' a scalar numeric value.' &.> ' is not';' represents' sayIsNumericScalar=: , TXT {::~ isNumericScalar</lang> Examples of use: <lang j> 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.</lang>
Java
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. <lang java>public boolean isNumeric(String input) {
try {
Integer.parseInt(input);
return true;
}
catch (NumberFormatException e) {
// s is not numeric
return false;
}
}</lang>
Alternative 1 : Check that each character in the string is number. Note that this will only works for integers.
<lang java>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
}</lang>
Alternative 2 : use a regular expression (a more elegant solution).
<lang java>public static boolean isNumeric(String inputData) {
return inputData.matches("[-+]?\\d+(\\.\\d+)?");
}</lang>
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.
<lang java>public static boolean isNumeric(String inputData) {
NumberFormat formatter = NumberFormat.getInstance(); ParsePosition pos = new ParsePosition(0); formatter.parse(inputData, pos); return inputData.length() == pos.getIndex();
}</lang>
Alternative 4 : use the java.util.Scanner object. Very useful if you have to scan multiple entries.
<lang java>public static boolean isNumeric(String inputData) {
Scanner sc = new Scanner(inputData); return sc.hasNextInt();
}</lang> 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] <lang javascript>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')} </lang>
jq
In versions of jq that support try/catch, the simplest way to test if a string can be parsed as a number is:<lang jq>try tonumber catch false</lang> 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: <lang jq>def is_numeric: true and try tonumber catch false;</lang>
Julia
The function isnumeric 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.
<lang julia>using Printf
isnumeric(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 = isnumeric(t) ? "is" : "is not"
@printf("%35s %s a direct numeric literal.\n", t, fl)
end</lang>
- 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
<lang scala>// 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 ${if (isNumeric(input)) "numeric" else "not numeric"}")
}</lang>
- Output:
152 is numeric -3.1415926 is numeric Foo123 is not numeric -0 is numeric 456bar is not numeric 1.0E10 is numeric
LabVIEW
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
Lasso
<lang Lasso>local(str='12345') string_isNumeric(#str) // true</lang>
<lang Lasso>'12345'->isdigit // true '1X34Q'->isdigit // false</lang>
Liberty BASIC
<lang lb> DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0" DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"
while n$ <> "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
</lang>
Lisaac
<lang Lisaac> "123457".is_integer.println; // write TRUE on stdin </lang>
Logo
<lang logo>show number? "-1.23 ; true</lang>
Lua
This will also accept strings like "0xFF" or "314.16e-2" as numbers. <lang lua>if tonumber(a) ~= nil then
--it's a number
end; </lang>
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$(1.2, "#.00") maybe return 1.20 or 1,20. The reverse function is Val() which can take more characters so A Val("121mm") is 121, and with a second parameter we can interpret properly the decimal dot: Print Val("1.2", ".") always return 1.2 double. Print Val("1,2", ",")=1.2 return true, 1.2 is a m2000 number literal and always has a dot. <lang M2000 Interpreter> \\ version 2 Module Checkit {
function global isNumber(a$, 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
</lang>
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.
<lang M2000 Interpreter> 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")
</lang>
Maple
<lang 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:</lang>
Mathematica / Wolfram Language
<lang Mathematica>NumberQ[ToExpression["02553352000242"]]</lang>
MATLAB
<lang 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
</lang>
Maxima
<lang maxima>numberp(parse_string("170141183460469231731687303715884105727"));</lang>
MAXScript
<lang maxscript>fn isNumeric str = (
try
(
(str as integer) != undefined
)
catch(false)
)
isNumeric "123"</lang>
min
<lang min>(
dup (((int integer?) (pop false)) try) dip ((float float?) (pop false)) try or
) :numeric?</lang>
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.
<lang MiniScript>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")</lang>
- Output:
1 1 1 1 0
MIPS Assembly
<lang mips>
- $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 </lang>
Mirah
<lang 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')</lang>
mIRC Scripting Language
<lang mirc>var %value = 3 if (%value isnum) {
echo -s %value is numeric.
}</lang>
Modula-3
<lang modula3>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.</lang>
- 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
<lang Nanoquery>def isNum(str)
try
double(str)
return true
catch
return false
end
end</lang>
Nemerle
<lang 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))");
}
}</lang>
NetRexx
<lang 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
</lang>
- 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
<lang 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"</lang>
We could prefer to use the “parsutils” module which avoids the exception:
<lang Nim>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"</lang>
- Output:
1 is numeric 3.14 is numeric -100 is numeric 1e2 is numeric Inf is numeric rose is not numeric
Objective-C
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.
<lang objc>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</lang>
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.
<lang objc>BOOL isNumeric(NSString *s) {
NSScanner *sc = [NSScanner scannerWithString: s];
if ( [sc scanFloat:NULL] )
{
return [sc isAtEnd];
}
return NO;
}</lang>
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).
<lang objc>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;
}</lang>
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:
<lang ocaml>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</lang>
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.
<lang octave>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</lang>
Oz
<lang oz>fun {IsNumeric S}
{String.isInt S} orelse {String.isFloat S}
end</lang>
PARI/GP
<lang parigp>isNumeric(s)={
my(t=type(eval(s))); t == "t_INT" || t == "T_REAL"
};</lang>
Pascal
See Delphi or Free Pascal.
PeopleCode
<lang 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; </lang>
Perl
<lang perl>use Scalar::Util qw(looks_like_number); print looks_like_number($str) ? "numeric" : "not numeric\n";</lang>
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.
<lang perl>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" }</lang>
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?
<lang perl>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]) }</lang>
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
<lang php><?php $string = '123'; if(is_numeric(trim($string))) { } ?></lang>
PicoLisp
The 'format' function can be used for that. It returns NIL if the given string is not a legal number <lang PicoLisp>: (format "123") -> 123
- (format "123a45")
-> NIL
- (format "-123.45" 4)
-> 1234500</lang>
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.
<lang Pike> 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 </lang>
PL/I
<lang 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;</lang>
5 '1'B 6.7 '1'B -8.9 '1'B -4e3 '1'B 4A37 '0'B
PL/SQL
<lang plsql>FUNCTION IsNumeric( value IN VARCHAR2 ) RETURN BOOLEAN IS
help NUMBER;
BEGIN
help := to_number( value ); return( TRUE );
EXCEPTION
WHEN others THEN return( FALSE );
END;</lang>
<lang plsql>Value VARCHAR2( 10 ) := '123'; IF( IsNumeric( Value ) )
THEN NULL;
END IF;</lang>
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.
<lang plainenglish>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.</lang>
- 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. <lang powershell>function isNumeric ($x) {
try {
0 + $x | Out-Null
return $true
} catch {
return $false
}
}</lang>
But this one doesn't work for strings like "8." though a . is appended it returns true!
Alternatively, you can use the static System.Int32.TryParse() method in the .NET framework.
<lang powershell>function isNumeric ($x) {
$x2 = 0 $isNum = [System.Int32]::TryParse($x, [ref]$x2) return $isNum
}</lang>
Prolog
The code:
<lang prolog>numeric_string(String) :-
atom_string(Atom, String), atom_number(Atom, _).</lang>
A predicate to test the code:
<lang prolog>test_strings(Strings) :-
forall( member(String, Strings),
( ( numeric_string(String)
-> Result = a
; Result = 'not a' ),
format('~w is ~w number.~n', [String, Result])
)
).</lang>
Example of using the test predicate:
<lang prolog>?- 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.</lang>
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. <lang PureBasic>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</lang>
- Output:
'+3183.31151E+321' = 1 '-123456789' = 1 '123.45.6789+' = 0 '-e' = 0
Python
Python: Simple int/float
<lang python>def is_numeric(s):
try:
float(s)
return True
except (ValueError, TypeError):
return False
is_numeric('123.0')</lang>
Or for positive integers only:
<lang python>'123'.isdigit()</lang>
Python: Most numeric literals
Including complex, hex, binary, and octal numeric literals we get: <lang python>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</lang>
Sample use, including value parsed, its type, and standard method str.isnumeric(): <lang python>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() ))</lang>
- 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
Quackery
<lang 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</lang>
- Output:
152 is a valid number. -3.1415926 is a valid number. Foo123 is not a valid number.
R
<lang R>> strings <- c("152", "-3.1415926", "Foo123") > suppressWarnings(!is.na(as.numeric(strings))) [1] TRUE TRUE FALSE </lang>
Racket
<lang racket>(define (string-numeric? s) (number? (string->number s)))</lang> Or, since all non-#f are true: <lang racket>(define string-numeric? string->number)</lang>
Raku
(formerly Perl 6)
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.
<lang perl6>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;</lang>
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
<lang 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 </lang>
REBOL
<lang 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]] </lang>
Retro
Retro does not have floating point numbers as part of the core system. For others, this can be done with:
<lang Retro>'123 a:from-string TRUE [ swap c:digit? and ] a:reduce</lang>
REXX
<lang rexx>/*REXX program to determine if a string is numeric. */ 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=' +6 ' zzz=' + 7 ' zzz=' - 8 ' zzz=' - .9 ' zzz='- 19.' 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 ' ifx=i
/*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,'nim.') 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 arg. */
/*note: some REXX interpreters don't support the ¬ (not) character.*/ /*note: " " " " " the / as negation. */</lang>
Ring
<lang ring> see isdigit("0123456789") + nl + # print 1
isdigit("0123a") # print 0
</lang>
Ruby
<lang ruby>def is_numeric?(s)
begin Float(s) rescue false # not numeric else true # numeric end
end</lang>
or more compact:
<lang ruby>def is_numeric?(s)
!!Float(s) rescue false
end</lang>
NB! Since Ruby 2.6 you no longer need `rescue`:
<lang ruby>def is_numeric?(s)
!!Float(s, exception: false)
end</lang>
Adding `exception: false` will make it return `nil` instead.
sample <lang ruby>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</lang>
- 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
<lang runbasic>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</lang>
123 1 1ab 0
Rust
<lang 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()
}</lang>
Scala
<lang scala> import scala.util.control.Exception.allCatch
def isNumber(s: String): Boolean = (allCatch opt s.toDouble).isDefined </lang>
<lang scala> def isNumeric(input: String): Boolean = input.forall(_.isDigit) </lang>
Or a more complete version, using a complex regular expression: <lang scala> def isNumeric2(str: String): Boolean = {
str.matches(s"""[+-]?((\d+(e\d+)?[lL]?)|(((\d+(\.\d*)?)|(\.\d+))(e\d+)?[fF]?))""")
} </lang>
Or using the built-in number parsing and catching exceptions: <lang scala> def isNumeric(str: String): Boolean = {
!throwsNumberFormatException(str.toLong) || !throwsNumberFormatException(str.toDouble)
}
def throwsNumberFormatException(f: => Any): Boolean = {
try { f; false } catch { case e: NumberFormatException => true }
} </lang>
Scheme
string->number returns #f when the string is not numeric and otherwise the number, which is non-#f and therefore true. <lang scheme>(define (numeric? s) (string->number s))</lang>
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.
<lang seed7>$ 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;</lang>
Sidef
There is the the String.looks_like_number method, which returns true when a given strings looks like a number: <lang ruby>say "0.1E-5".looks_like_number; #=> true</lang>
Alternatively, we can use regular expressions to determine this:
<lang ruby>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/)
}</lang>
Sample: <lang ruby>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)))
}</lang>
- 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.
<lang simula>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 </lang>
- 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
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...
<lang smalltalk>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 ]</lang>
(should work with all) <lang smalltalk>(Number readFrom:(aString readStream) onError:[nil]) notNil</lang> to handle radix numbers (such as 2r10111), use: <lang smalltalk>(Scanner scanNumberFrom:(aString readStream)) notNil</lang>
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.
<lang Snobol4> 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</lang>
- Output:
T: 123 T: 123.0 T: 123. T: -123 T: 3.14159 F: 1.2.3 F: abc F: A440
SQL
<lang sql>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'</lang>
SQL PL
version 9.7 or higher.
With SQL PL: <lang 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(' ')@ </lang> 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
<lang sml>(* 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</lang>
Swift
<lang swift>func isNumeric(a: String) -> Bool {
return Double(a) != nil
}</lang>
This one only checks whether it is an integer: <lang swift>func isNumeric(a: String) -> Bool {
return a.toInt() != nil
}</lang>
Tcl
<lang tcl>proc isNumeric str {string is double -strict $str}</lang>
TMG
Unix TMG dialect. NOTE: the program also performs some basic normalization (namely, removing the plus sign and translating "E" to "e"): <lang UnixTMG>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: !<< >>;</lang>
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.
<lang toka>[ ( 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 )</lang>
UNIX Shell
<lang bash>
- !/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 </lang>
- 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
<lang ursa>def isnum (string str) try double str return true catch valueerror return false end try end isnum</lang>
VBA
In France, IsNumeric("123.45") return False. So we have to check the "." or "," and replace it by the Application.DecimalSeparator.
<lang vb>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</lang>
VBScript
<lang vb>IsNumeric(Expr)</lang>
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. <lang vedit>:IS_NUMERIC: if (Num_Eval(SUPPRESS)==0 && Cur_Char != '0') {
Return(FALSE)
} else {
Return(TRUE)
}</lang>
Visual Basic .NET
<lang vbnet>Dim Value As String = "+123"
If IsNumeric(Value) Then
PRINT "It is numeric."
End If</lang>
Wren
Wren's Num class already has a static method which does what this task requires. <lang ecmascript>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")")
}</lang>
- 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'. <lang xlisp>(DEFUN NUMERICP (X)
(IF (STRING->NUMBER X) T))</lang>
zkl
<lang zkl>fcn isNum(text){
try{ text.toInt(); True }
catch{ try{ text.toFloat(); True }
catch{ False }
}
}</lang>
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
<lang 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
</lang>
Zoea Visual
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