Empty string: Difference between revisions

 

=={{header|11l}}==

I s.empty

print(‘String s is empty.’)

I !s.empty

 

=={{header|6502 Assembly}}==

An empty string is just a null terminator with no text in front.

 

Checking if a string is empty is simple, just count the number of characters before you reach the terminator. If that count equals zero, the string is empty. Otherwise, the string is not empty.

 

sta $00

lda #>EmptyString

cpy #0

beq StringIsEmpty ;if this branch is taken, the string is empty

 

=={{header|68000 Assembly}}==

{{trans|6502 Assembly}}

An empty string is just a null terminator with no text in front.

DC.B 0

Checking if a string is empty is simple, just count the number of characters before you reach the terminator. If that count equals zero, the string is empty. Otherwise, the string is not empty.

 

getStringLength:

CMP.L A0,(SP) ;compare the current A0 with the original value.

BEQ StringIsEmpty ;if they are equal, then nothing was read besides the terminator. Therefore the string is empty.

 

=={{header|8th}}==

Assign an empty string to a variable:

 

Check that the string is empty:

 

The check for a non-empty string is the same, but with "not" after the n:=

Declare an empty string at address <code>str</code>:

 

 

Check if a string stored at <code>x0</code> is empty:

 

ldrb w5, [x0]

 

Full program demo:

{{works with|aarch64-linux-gnu-as/qemu-aarch64}}

 

.equ SVC_WRITE, 64

.equ SVC_EXIT, 93

_exit:

mov x8, #SVC_EXIT

 

=={{header|ACL2}}==

To check if a string is empty:

 

=={{header|Action!}}==

PrintF("'%S' is empty? ",s)

IF s(0)=0 THEN

CheckIsEmpty(str1)

CheckIsEmpty(str2)

{{out}}

[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Empty_string.png Screenshot from Atari 8-bit computer]

=={{header|Ada}}==

 

 

function Is_Empty(S: String) return Boolean is

raise Program_Error with "something went wrong very very badly!!!";

end if;

 

=={{header|Aime}}==

s = "";

if (length(s) == 0) {

if (length(s) != 0) {

....

 

=={{header|ALGOL 68}}==

{{works with|ALGOL 68G|Any - tested with release 2.8.win32}}

STRING s := "";

 

# as a string is an array of characters, we could also test for emptyness by #

# checking for lower bound > upper bound #

 

=={{header|Apex}}==

String.isBlank(record.txt_Field__c);

--Returns true if the specified String is white space, empty (''), or null; otherwise, returns false.

 

=={{header|APL}}==

⍝⍝ Assign empty string to A

A ← ''

~0 = ⍴∊ A

0

 

=={{header|AppleScript}}==

-- assign empty string to str

set str to ""

-- str is not empty

end if

 

=={{header|ARM Assembly}}==

{{works with|as|Raspberry Pi}}

 

/* ARM assembly Raspberry PI */

 

 

=={{header|Arturo}}==

 

 

if empty? s -> print "the string is empty"

 

if not? empty? s -> print "the string is not empty"

 

{{out}}

 

=={{header|Asymptote}}==

if (length(c) == 0) {

write("Empty string");

} else {

write("Empty string");

{{out}}

<pre>Empty string

AutoHotkey has both "Traditional" or literal text, and "Expression" mode.

This code demonstrates the task using both methods.

; Assign an empty string:

var =

; Check that a string is not empty

If (var != "")

 

=={{header|Avail}}==

The type string is defined as <code><character…|></code> (a tuple of characters), so the empty tuple and the empty string are equivalent values, and all tuple/collection methods can be used on strings.

 

Assert: emptyStringVar = "";

Assert: emptyStringVar = <>;

Assert: emptyStringVar is empty;

 

Checking that a string is _not_ empty generally isn't any more interesting, just a logical negation of the above tests.

 

Assert: nonemptyStringVar ≠ "";

Assert: nonemptyStringVar ≠ <>;

Assert: ¬nonemptyStringVar is empty;

 

The library also defines a type _nonempty string_, which can be leveraged for a type-membership check.

 

 

=={{header|AWK}}==

BEGIN {

# Demonstrate how to assign an empty string to a variable.

print "Is b empty ?",length(b)==0;

print "Is b not empty ?",length(b)!=0;

{{out}}

<pre>$ awk -f R/tmp/string.awk

 

=={{header|Axe}}==

!If length(Str1)

Disp "EMPTY",i

Else

Disp "NOT EMPTY",i

 

=={{header|BASIC}}==

 

20 IF A$="" THEN PRINT "THE STRING IS EMPTY"

30 IF A$<>"" THEN PRINT "THE STRING IS NOT EMPTY"

 

==={{header|Applesoft BASIC}}===

The terminating quote may be left off. By default, strings are initially empty so the assignment is not necessary. Another way to check for an empty string is to use the LEN function.

40 IF LEN (A$) = 0 THEN PRINT "THE STRING IS EMPTY"

 

==={{header|BaCon}}===

The literal empty string in BaCon is <tt>""</tt>.

 

a$ = ""

IF a$ = "" THEN PRINT "Empty string"

 

There are other ways, such as a zero return from the <tt>LEN(s$)</tt> or <tt>ULEN(utf$)</tt> functions. <tt>EQUAL(s$, "")</tt> would be another way.

 

==={{header|BASIC256}}===

if length(s$) = 0 then

print "String is empty"

u$ = "not empty"

call IsEmpty (u$)

 

==={{header|IS-BASIC}}===

20 IF A$="" THEN PRINT "The string is empty."

 

==={{header|QB64}}===

If a$ = "" Then Print "Empty String"

 

==={{header|QBasic}}===

IF LEN(s) = 0 THEN

PRINT "String is empty"

IsEmpty (t$)

u$ = "not empty"

 

==={{header|True BASIC}}===

IF Len(s$) = 0 THEN

PRINT "String is empty"

LET u$ = "not empty"

CALL IsEmpty(u$)

 

==={{header|uBasic/4tH}}===

Print Show(FUNC(_IsEmpty(t)))

u := "not empty"

End

 

==={{header|Yabasic}}===

if len(s$) = 0 then

print "String is empty"

u$ = "not empty"

IsEmpty (u$)

 

=={{header|Batch File}}==

@echo off

 

::Alternatively,

if %var%@ neq @ echo Var is not a blank string.

 

=={{header|BBC BASIC}}==

var$ = ""

REM Check that a string is not empty:

IF var$ <> "" THEN PRINT "String is not empty"

 

=={{header|BQN}}==

To check emptiness, we can check the length of the array using <code>≠</code> (or shape with <code>≢</code>).

 

•Show 0 = ≠ ""

•Show 0 ≠ ≠ ""

⟨⟩

1

0

 

=={{header|Bracmat}}==

There are two ways to assign a string to a variable. The variant using the <code>=</code> operator does not evaluate the value before the assignment, the variant using the <code>:</code> (match) operator does. If the value is a string, there is no difference, as a string always evaluates to itself.

& (b=)

& abra:?c

& !d:~ { neither is d an empty string }

)

 

=={{header|Burlesque}}==

Empty string is <tt>""</tt> and checking for empty strings (or empty lists) can be done with the <tt>nu</tt> command.

 

blsq ) ""

""

blsq ) "a"nu

0

 

=={{header|C}}==

In C the strings are <code>char</code> pointers. A string terminates with the null char (U+0000, <code>'\0'</code>), which is not considered part of the string. Thus an empty string is <code>"\0"</code>, while a null string is a null pointer which points to nothing.

 

/* ... */

/* or compare to a known empty string, same thing. "== 0" means strings are equal */

if (strcmp(str, "") == 0) { ... }

 

=={{header|C sharp|C#}}==

 

class Program {

if (!string.IsNullOrEmpty(example)) { }

}

 

===In depth===

Note: implementation information provided in comments was obtained reflecting .NET libraries and viewing the .NET Core reference source and may not be correct or remain relevant as time passes.

 

using System.Collections.Generic;

 

P(!EqualityComparer<string>.Default.Equals(s, ""));

}

 

=={{header|C++}}==

 

// ...

// create empty string as default parameter

void func( std::string& s = {} ); // {} generated default std:string instance

 

=={{header|Caché ObjectScript}}==

; Demonstrate how to assign an empty string to a variable.

set x = ""

write !,"String length: "_$length(x)_", Equals null: "_(x = "")_", Empty pattern: "_(x?."")

 

{{out}}SAMPLES>do EMPTYSTR^ROSETTA

 

=={{header|Clojure}}==

(def x "") ;x is "globally" declared to be the empty string

(let [x ""]

(= x "") ;true if x is the empty string

(not= x "") ;true if x is not the empty string

 

=={{header|COBOL}}==

IDENTIFICATION DIVISION.

PROGRAM-ID. EMPTYSTR.

 

STOP RUN.

 

=={{header|CoffeeScript}}==

Empty strings are mostly straightforward in CoffeeScript, but there's one gotcha.

 

isEmptyString = (s) ->

# Returns true iff s is an empty string.

console.log (s = '') == "" # true

console.log new String() == '' # false, due to underlying JavaScript's distinction between objects and primitives

 

=={{header|Common Lisp}}==

Common Lisp treats empty strings as true (T in Common Lisp), therefore one must check the length of the string to know if it is empty or not.

(defparameter *s* "") ;; Binds dynamic variable *S* to the empty string ""

(let ((s "")) ;; Binds the lexical variable S to the empty string ""

(typep s '(and string

(not (string 0))))) ;; only returns true on string that is not empty

 

=={{header|Component Pascal}}==

BlackBox Component Builder

MODULE EmptyString;

IMPORT StdLog;

END Do;

END EmptyString.

Execute: ^Q EmptyString.Do<br/>

{{out}}

=={{header|D}}==

D treats null strings and empty strings as equal on the value level, but different on object level. You need to take this into account when checking for emptiness.

 

bool isEmptyNotNull(in string s) pure nothrow @safe {

assert(s1.empty);

assert(s2.isEmptyNotNull());

 

=={{header|Dart}}==

 

var empty = '';

 

print('it is not empty');

}

 

=={{header|Delphi}}==

 

{$APPTYPE CONSOLE}

s := 'abc';

Writeln(StringIsEmpty(s)); // False

 

=={{header|Diego}}==

Assign an empty string to variable <code>s</code>.

 

Check a string is empty (various approaches).

add_bool(isEmpty)

()_check⟦[es]==⟦⟧⟧;

;

log_console()_(isEmpty);

 

{{out}}

 

Check a string is not empty (various approaches).

add_bool(isNotEmpty)

()_check⟦[s]!=⟦⟧⟧;

;

log_console()_(isNotEmpty);

 

{{out}}

 

Check a string is <code>null</code> (␀) (various approaches).

add_bool(isNull)

()_check⟦![n]⟧;

(n)_equal⟦␀⟧;

;

 

{{out}}

 

=={{header|DWScript}}==

 

s := ''; // assign an empty string (can also use "")

 

if s <> '' then

 

=={{header|Dyalect}}==

Demonstrate how to assign an empty string to a variable:

 

 

Demonstrate how to check that a string is empty:

 

 

Demonstrate how to check that a string is not empty:

 

 

=={{header|Déjà Vu}}==

Like in Python, empty strings are falsy, non-empty strings are truthy.

 

if not e:

 

if e:

 

=={{header|EasyLang}}==

 

if a$ = ""

print "empty"

if a$ <> ""

print "no empty"

 

=={{header|Elena}}==

ELENA 4.x:

public program()

if (s.isNonempty())

{ console.printLine("'", s, "' is not empty") }

{{out}}

<pre>

=={{header|Elixir}}==

To check whether a given variable holds an empty string, either compare it to the empty string literal, check its length - O(M), or check it's byte size - O(1)).

empty_string = ""

not_empty_string = "a"

byte_size(not_empty_string) == 0

# => false

 

=={{header|Emacs Lisp}}==

 

(if (= 0 (length str))

(message "string is empty"))

(if (/= 0 (length str))

 

Also possible is <code>(string= "" str)</code>.

 

=={{header|Erlang}}==

1> S = "". % erlang strings are actually lists, so the empty string is the same as the empty list [].

[]

4> case "aoeu" of [] -> empty; [H|T] -> not_empty end.

not_empty

 

=={{header|Euphoria}}==

 

-- assign an empty string

if length(s) then

-- string is not empty

 

=={{header|F_Sharp|F#}}==

 

[<EntryPoint>]

printfn "Is empty %A: %A" emptyString (emptyString = String.Empty)

printfn "Is not empty %A: %A" emptyString (emptyString <> String.Empty)

{{out}}

<pre>Is empty "": true

It's idiomatic in Factor to prefer using the stack over variable bindings.

 

{{out}}

<pre>

However, Factor provides lexical variables:

 

[let

"" :> empty-string

empty-string empty? .

empty-string empty? not .

{{out}}

<pre>

Fantom uses "" to represent an empty string, and provides the isEmpty method to check if a string is empty.

 

a := "" // assign an empty string to 'a'

a.isEmpty // method on sys::Str to check if string is empty

a == "" // alternate check for an empty string

!a.isEmpty // check that a string is not empty

 

=={{header|Forth}}==

Strings are represented as an addr-len pair on the stack. An empty string has len 0.

\ string words operate on the address and count left on the stack by a string

\ ? means the word returns a true/false flag on the stack

: filled? ( c-addr u -- ? ) empty? 0= ;

: ="" ( c-addr u -- ) drop 0 ; \ It's OK to copy syntax from other languages

 

Forth Console Test (True= -1, False=0)

 

Such variables, or text literals, may be passed as a parameter to a subprogram, and it may use the LEN function to ascertain the size of the parameter, which in that sense could be considered a string because CHARACTER parameters are passed with a secret additional parameter, their size, which is available to the LEN function within the subprogram.

CHARACTER*(*) T !This form allows for any size.

IF (LEN(T).LE.0) WRITE(6,*) "Empty!"

TEXT = "" !Fills the entire variable with space characters.

CALL TASTE(TEXT) !Passes all 24 of them. Result is Not empty!

Otherwise, you could employ the Fortran protocol that trailing spaces are irrelevant in text comparisons. Thus <code>TEXT .EQ. ""</code> would give ''true'' even though TEXT might contain thousands of space characters, and so would <code>TEXT .EQ. " "</code> - thus an empty string is one containing nothing other than spaces.

 

=={{header|Free Pascal}}==

Assigning an empty string:

Checking for an empty string:

Checking for a non-empty string:

length(s) > 0

The <code>sysUtils</code> unit defines the constants <code>emptyStr</code> and <code>emptyWideStr</code>, which can be used in place of <code>&#39;&#39;</code>.

 

=={{header|FreeBASIC}}==

 

Sub IsEmpty(s As String)

Dim u As String = "not empty"

IsEmpty(u)

 

{{out}}

 

=={{header|Frink}}==

if a == ""

println["empty"]

 

if a != ""

 

=={{header|FutureBasic}}==

 

CFStringRef s

if ( len(s) != 0 ) then print @"string not empty"

 

 

=={{header|Gambas}}==

'''[https://gambas-playground.proko.eu/?gist=4d8a208f49364dc25361bf2042af1005 Click this link to run this code]'''

Dim sString As String[] = ["", "Hello", "world", "", "Today", "Tomorrow", "", "", "End!"]

Dim sTemp As String

Next

 

Output:

<pre>

In Go variables are always initialized to a provided value or to the "zero value" of the type.

The zero value of a string is the empty string.

var s string

s2 := ""

// check that a string is not empty, any of:

s != ""

 

import (

// check that a string is not empty.

test(str2) // prt not empty

 

=={{header|Groovy}}==

assert s.empty

 

s = '1 is the loneliest number'

 

=={{header|GW-BASIC}}==

20 S2$ = "" 'explicitly defined empty string

30 S3$ = "Foo bar baz"

70 END

200 IF LEN(S$)=0 THEN PRINT "Empty string" ELSE PRINT "Non-empty string"

 

=={{header|Harbour}}==

// we can also use comparison expressions like [cString == ""] and [cString != ""], yet the most convenient

// of them is `Empty()` (but that depends on personal coding style).

IF ! Empty( cString ) // --> FALSE

? cString

 

=={{header|Haskell}}==

 

-- In Haskell strings are just lists (of characters), so we can use the function

let s = ""

when (null s) (putStrLn "Empty.")

 

=={{header|HolyC}}==

U8 *str = StrNew("");

/* or */

 

/* to test if string is not empty */

 

=={{header|i}}==

s = ""

end

}

 

=={{header|Icon}} and {{header|Unicon}}==

Icon and Unicon can produce empty strings in several ways:

s := string('A'--'A') # ... converted from cset difference

s := char(0)[0:0] # ... by slicing

s := &null # NOT a null string, null type

/s # test for null type

 

=={{header|J}}==

 

0=#variable

1

0<#variable

 

Note that J attempts to make no distinction between empty lists, regardless of their type. In other words, while some operations can reveal the type of an empty list (for example, anything that can introduce padding based on the type of the list itself) this distinction is ignored whenever possible. You can perform arithmetic on an empty string, and you can append text to an empty list of numbers even though these operations would not succeed on non-empty lists of the same type.

example:

 

 

EMPTY

0

$EMPTY

 

Here, the display of an empty string occupies one line (just like the display of any other string -- except this line is an empty line), while the display of <code>EMPTY</code> occupies zero blank lines. Or <code>EMPTY</code> contains zero empty strings (or zero empty lists). When you want the result of a J verb to not display any result, use a value like EMPTY as its explicit result.

=={{header|Java}}==

<code>String.isEmpty()</code> is part of Java 1.6. Other options for previous versions are noted.

if(s != null && s.isEmpty()){//optionally, instead of "s.isEmpty()": "s.length() == 0" or "s.equals("")"

System.out.println("s is empty");

}else{

System.out.println("s is not empty");

 

=={{header|JavaScript}}==

Create an empty String

 

Boolean expressions representing emptiness

s.length == 0

!s

 

Non-emptiness

s != ""

s.length != 0

s.length > 0

 

=={{header|jq}}==

 

# or:

# or:

 

=={{header|Jsish}}==

var em1 = '';

var em2 = new String();

(em1 === em2) ==> true

=!EXPECTEND!=

 

{{out}}

 

=={{header|Julia}}==

blank = ""

nonblank = "!"

println("That nonblank is empty is ", isempty(nonblank))

println("That nonblank is not empty is ", !isempty(nonblank))

 

{{out}}

{{trans|J}}

 

0=#variable

1

0<#variable

 

=={{header|Kotlin}}==

val s = ""

println(s.isEmpty()) // true

println(s.none()) // true

println(s.any()) // false

 

=={{header|LabVIEW}}==

=={{header|Lambdatalk}}==

In Lambdatalk primitives working on sequences of words begin with "S."

'{def emptyString }

-> emptyString

'{= {S.length {emptyString}} 0}

-> true

 

=={{header|langur}}==

You can use empty quote marks or the ZLS token.

writeln .zls == ""

writeln .zls != ""

 

{{out}}

 

=={{header|Lasso}}==

local(str = string)

local(str = '')

local(str = 'Hello, World!')

#str->size > 0 // true

 

=={{header|Latitude}}==

 

Assigning the empty string.

 

Checking whether a string is empty.

s empty?.

 

Note that all strings are truthy in Latitude, so simply checking the truthiness of a string is an insufficient means to check whether it is empty.

{{trans|Erlang}}

 

> (set str "")

()

> (case "apple" ('() 'empty) ((cons head tail) 'not-empty))

not-empty

 

=={{header|Lhogho}}==

Lhogho is a Logo compiler for Windows and Linux

print empty? :str ;prints 'true'

print not empty? :str ;prints 'false'

 

=={{header|Liberty BASIC}}==

'assign empty string to variable

a$ = ""

if a$<>"" then print "Not empty."

if len(a$)>0 then print "Not empty."

 

=={{header|Lingo}}==

put str=EMPTY

-- 1

put str<>EMPTY

 

=={{header|LOLCODE}}==

The empty string is a false value in LOLCODE, and is thus amenable to use as the condition of an <tt>O RLY?</tt>

 

I HAS A string ITZ ""

OIC

 

 

=={{header|Lua}}==

-- create an empty string 3 different ways

str = ""

end

 

 

=={{header|M2000 Interpreter}}==

Easy reply for this task

A$=""

Print A$<>"", A$="", Len(A$)=0

 

Depends of variable visibility, and what we want to do: To make a new local, to shadow a local or a global on.

 

Module Checkit {

\\

}

Checkit

 

=={{header|Maple}}==

s := ""; # Create an empty string

evalb(s = ""); # test if the string is empty

evalb(s <> ""); # test if the string is not empty

 

=={{header|Mathematica}} / {{header|Wolfram Language}}==

str=""; (*Create*)

str==="" (*test empty*)

str=!="" (*test not empty*)

 

=={{header|MATLAB}} / {{header|Octave}}==

 

str = '';

% Demonstrate how to check that a string is empty.

% Demonstrate how to check that a string is not empty.

~isempty(str)

 

=={{header|Maxima}}==

 

/* check using string contents */

/* check using string length */

slength(s) = "";

 

=={{header|Mercury}}==

There's nothing special about empty strings in Mercury.

 

 

( if S = "" then ... else ... ), % checking if a string is empty

 

 

=={{header|min}}==

{{works with|min|0.19.3}}

The <code>bool</code> operator returns <code>false</code> on an empty string and <code>true</code> on a non-empty string. We can define <code>empty?</code> as the negation of <code>bool</code>.

"" empty? puts!

{{out}}

<pre>

 

Storing an empty string:

la a0,UserRam

 

Checking that a string is (not) empty:

 

nop ;load delay slot (only necessary on MIPS I hardware)

beqz t0,StringIsEmpty

nop ;branch delay slot

 

 

=={{header|Mirah}}==

empty_string2 = String.new

 

puts "empty string is empty" if empty_string1.isEmpty()

puts "empty string has no length" if empty_string2.length() == 0

 

=={{header|Modula-3}}==

 

IMPORT IO,Text;

(* To check for a non-empty string, negate any of the above

conditions with NOT *)

 

=={{header|Nanoquery}}==

 

if len(s)=0

else

println "s is not empty"

 

=={{header|Nemerle}}==

Assign an empty string:

Check if a string is empty/not empty:

 

=={{header|NESL}}==

 

% To make sure it is empty, we can ask whether its length is equal to zero. %

 

{{out}}

<pre>my_empty_string = "" : [char]

 

=={{header|NetRexx}}==

options replace format comments java crossref symbols binary

 

 

return

{{out}}

<pre>

 

=={{header|Nim}}==

 

if x == "":

echo "empty"

if x.len > 0:

 

=={{header|NS-HUBASIC}}==

20 IF S$<>"" THEN O$="NOT "

 

=={{header|Nyquist}}==

===Lisp Syntax===

(setf emptystring "") ;binds variable'emptystring' to the empty string ""

 

(when (and (stringp emptystring)(> (length emptystring) 0))

(print "Is a non-empty string")))

 

===SAL Syntax===

define variable emptystring = "" ;binds variable'emptystring' to the empty string ""

 

else

print "is not empty string"

 

 

===Audacity plug-in (LISP syntax)===

;nyquist plug-in

;version 4

"The string is empty."

"The string is not empty.")

 

 

===Audacity plug-in (SAL syntax)===

;nyquist plug-in

;version 4

"The string is empty.",

"The string is not empty.")

 

=={{header|oberon-2}}==

{{works with|oo2c version 2}}

MODULE EmptyString;

IMPORT Out;

Out.String("checking str[0] = 0X. Is Empty? ");Out.Bool(str[0] = 0X);Out.Ln;

END EmptyString.

{{out}}

<pre>

 

=={{header|Objeck}}==

s := "";

if(s->IsEmpty()) {

"s is not empty"->PrintLine();

};

 

=={{header|OCaml}}==

 

(s = "")

 

Printf.printf "s1 empty? %B\n" (is_string_empty s1);

Printf.printf "s2 empty? %B\n" (is_string_empty s2);

 

{{out}}

isEmpty can be used on all collections, not only strings.

 

 

=={{header|Ol}}==

 

; define the empty string

(define empty-string "")

(less? 0 (string-length the-string)))

(print "the-string is NOT empty))

 

=={{header|ooRexx}}==

should work with each and every REXX interpreter/compiler.

w=' '

if v=='' Then Say 'v contains the empty string'<

If length(w)>0 Then Say 'Variable w does not contain the empty string'

{{out}}

<pre>v contains the empty string

Strings can be stored in CHARACTER and LONGCHAR variables. Both are initially empty. Both can also be unknown. A CHARACTER has a maximum length of approx 32000 bytes.

 

 

IF cc > '' THEN

ELSE /* IF cc = '' */

MESSAGE 'empty' VIEW-AS ALERT-BOX.

 

=={{header|PARI/GP}}==

isEmpty(s)=s=="" \\ Alternately:

isEmpty(s)=#s==0

isNonempty(s)=s!="" \\ Alternatively:

 

=={{header|Pascal}}==

''See also [[#Delphi|Delphi]] or [[#Free Pascal|Free Pascal]]''

{{works with|Extended Pascal}}

var

s: string(20);

{ you will need to call `trim` (remove trailing blanks) first. }

writeLn('trim(s) = '''' :':20, trim(s) = '':6)

{{out}}

EQ(s, '&#39;) : True

 

=={{header|Perl}}==

print "The string is empty";

}

if ($s ne "") { # Test for non empty string

print "The string is not empty";

 

In Perl, an empty string is often used to represent a false value.

if ($s) { ... } # false

 

# but a string that converts to number 0 is not always false, though:

$s = "0 but true";

 

=={{header|Phix}}==

{{libheader|Phix/basics}}

<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>

<span style="color: #004080;">string</span> <span style="color: #000000;">s</span>

<span style="color: #008080;">if</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">s</span><span style="color: #0000FF;">)!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- string is not empty</span>

<span style="color: #008080;">if</span> <span style="color: #000000;">s</span><span style="color: #0000FF;">!=</span><span style="color: #008000;">""</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- string is not empty</span>

 

=={{header|PHP}}==

 

$str = ''; // assign an empty string to a variable

 

if (strlen($str) == 0) { ... }

 

=={{header|Picat}}==

S = "", % assign an empty string to a variable

S == "", % check that a string is empty,

 

In Picat a string is a list of characters so list notation can be also be used.

S = "", % assign an empty string to a variable

S == [], % check that a string is empty,

 

=={{header|PicoLisp}}==

The empty string is represented by '[http://software-lab.de/doc/ref.html#nilSym NIL]' in PicoLisp. During input, two subsequent double quotes '""' return the symbol NIL.

(off String)

(setq String "")

(and String ..)

(if String ..)

 

=={{header|Pike}}==

string s;

 

 

return 0;

 

=={{header|PL/I}}==

s = ''; /* assign an empty string to a variable. */

if length(s) = 0 then ... /* To test whether a string is empty */

if length(s) > 0 then ... /* to test for a non-empty string */

 

=={{header|Plain English}}==

Start up.

Put "" into a string.

If the string is not blank, write "Not empty!" on the console.

Wait for the escape key.

 

=={{header|PowerShell}}==

Assignment (the type identifier is optional):

[string]$alpha = "abcdefghijklmnopqrstuvwxyz"

[string]$empty = ""

# or...

[string]$empty = [String]::Empty

Tests:

[String]::IsNullOrEmpty($alpha)

[String]::IsNullOrEmpty($empty)

{{Out}}

<pre>

=={{header|Prolog}}==

{{works with|SWI-Prolog|7}}

 

is_empty_string(String) :- String == "".

not_empty_string(String) :- String \== "".

 

=={{header|PureBasic}}==

In PureBasic we can just test a string for truth to determine if it has a value.

If a

ProcedureReturn "String is not empty, it contains '" + a + "'."

Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()

CloseConsole()

{{out}}

<pre>String is empty, or null.

Any non-empty ''string'', including '0', is always treated as True in a boolean context.

 

s = ''

# or:

elif s is None:

return True

 

=={{header|QB64}}==

If Len(s1) = 0 Then Print "Empty"

 

s3$ = "cat"

If Len(s3$) <> 0 Then Print "Not empty"

{{out}}

<pre>

Demonstrated as a dialogue in the Quackery REPL.

 

 

Enter "leave" to leave the shell.

...

 

 

=={{header|Quite BASIC}}==

20 if s="" then let o=""

30 if s<>"" then let o="not "

 

=={{header|R}}==

 

if (s == '') cat('Empty\n')

if (s != '') cat('Not empty\n')

#or

 

=={{header|Racket}}==

 

 

(define empty-string "")

(define (string-null? s) (string=? "" s))

 

=={{header|Raku}}==

(formerly Perl 6)

 

say 'String is empty' unless $s;

 

Unlike in Perl 5, only empty strings test as false - the string "0" tests as true now.

 

=={{header|Rascal}}==

if (s=="") print("string s is empty");

if (s!="") print("string s is not empty");

Or the build-in operator:

if (isEmpty(s)) print("string s is empty");

 

=={{header|Red}}==

s: copy "" ;; assign empty string

?? s

s: "abc"

prin s unless empty? s [print " not empty"]

{{out}}

<pre>s: ""

=={{header|Retro}}==

Create an empty string and assign it to a variable. In these '''keepString''' is used to ensure that the string is permanent.

( by creating a variable )

"" keepString variable: foo

( by setting an existing variable 'foo' )

"" keepString !foo

 

Checking that a string is empty. A string with a length of zero is assumed to be empty.

 

: emtpy? ( $-f ) getLength 0 = ;

 

"" empty? putn

"hello" empty? putn

 

Check that a string is not empty.

 

: notEmpty? ( $-f ) getLength 0 > ;

 

"" notEmpty? putn

"hello" notEmpty? putn

 

=={{header|REXX}}==

 

/*─────────────── 3 simple ways to assign an empty string to a variable.*/

if length(cod)\=0 then fish=cod /*a not-as-fast compare. */

 

 

=={{header|Ring}}==

cStr = NULL # empty string

if cStr = NULL

see "cstr is not empty string!" + nl

ok

 

=={{header|Robotic}}==

set "$string" to ""

if "$string.length" = 0 then "empty"

* "Empty string"

end

 

=={{header|Ruby}}==

 

Create an empty string

s = String.new

 

These expressions all evaluate to true to determine emptiness:

s.eql?("")

s.empty?

 

# also silly things like

 

Non-empty expressions, in addition to simply negating the above expressions:

s.length > 0

 

Note that we can '''not''' do the following, because the empty string is equivalent to true in Ruby ([[Boolean values#Ruby]]):

 

=={{header|Run BASIC}}==

' --------------

'empty string

' -------------

if var$<>"" then print "String Not empty."

 

=={{header|Rust}}==

println!("is empty: {}", s.is_empty());

let t = "x";

let b = "x".to_string();

println!("is empty: {}", b.is_empty());

 

=={{header|Scala}}==

val s=""

// check that string is empty

s.nonEmpty // false

s!="" // false

 

=={{header|Scheme}}==

(define (string-null? s) (string=? "" s))

 

=={{header|Seed7}}==

s := ""

 

 

# check that string is not empty

 

=={{header|Self}}==

"Put an empty string in a slot called 'str'"

str: ''.

"Check that string is not empty"

 

=={{header|SenseTalk}}==

set emptyString to ""

 

 

put emptyString is not empty

{{out}}

<pre>

=={{header|Sidef}}==

Create an empty string:

 

These expressions all evaluate to true to determine emptiness:

s.length == 0;

s.is_empty;

s ~~ /^\z/;

 

Non-empty expressions, in addition to simply negating the above expressions:

s.length > 0;

s ~~ /./s;

 

=={{header|Smalltalk}}==

str := ''.

 

str notEmpty

str size = 0

Notice that assignment is ":=" whereas equality check is "=".

 

=={{header|SNOBOL4}}==

An assignment statement with nothing to the right of the <tt>=</tt> operator assigns the empty string (or, as it is more commonly called in SNOBOL, the null string).

X =

* CHECK THAT X IS INDEED NULL

YES OUTPUT = 'NULL'

END

{{out}}

<pre>NULL</pre>

 

=={{header|Standard ML}}==

val s = ""

(* Check that a string is empty*)

s = ""

(* Check that a string is nonempty *)

 

=={{header|Stata}}==

 

display s==""

 

* Alternatively, check the length

 

=={{header|Swift}}==

if s.isEmpty { // alternately, s == ""

println("s is empty")

} else {

println("s is not empty")

 

=={{header|Tcl}}==

The only special position that the empty string has in Tcl is that a great many commands return it, and the REPL of [[tclsh]] and [[wish]] doesn't print it. Otherwise, it is just like any other value.

if {$s eq ""} {puts "s contains an empty string"}

There are other ways to check for emptiness and non-emptiness too (though the above are favored for reasons of simplicity, clarity and speed):

if {[string length $s] == 0} {puts "is empty"}

 

=={{header|TorqueScript}}==

 

=={{header|TUSCRIPT}}==

$$ MODE TUSCRIPT

s=""

IF (s=="") PRINT "s is an empty string"

IF (s!="") PRINT "s is a non-empty string"

{{out}}

<pre>

====Pattern Matching====

 

 

If <code>a</code> is unbound, a binding is created, containing the empty string.

====TXR Lisp====

 

 

(if (equal a "")

 

(if (zerop (length a))

 

=={{header|UNIX Shell}}==

 

s=""

 

# examine the length of the string

if [ -z "$s" ]; then echo "the string has length zero: it is empty"; fi

 

When using comparison operators, it is crucial to double-quote the variable within the conditional expression. This will ensure the shell sees the correct number of arguments. For example, if one were to write <tt>[ $s = "" ]</tt>, then after variable substitition, the shell will try to evaluate <tt>[ = "" ]</tt> which is a syntax error.

 

=={{header|Ursa}}==

set s ""

 

else

out "not empty" endl console

 

=={{header|VAX Assembly}}==

 

.entry empty, ^m<>

tstw desc ;check length field

;... empty

ret

 

=={{header|VBA}}==

dim s as string

 

'or:

if Len(s) > 0 then Debug.Print "not empty."

 

=={{header|VBScript}}==

 

===In brief===

 

' Assign empty string:

' Check for null or empty (more idiomatic in .NET):

If String.IsNullOrEmpty(s) Then

 

===In depth===

In .NET Core, functions defined in <code>Microsoft.VisualBasic</code> are only available for .NET Core 3.0 and above.

 

 

Module Program

P(Not EqualityComparer(Of String).Default.Equals(s, ""))

End Sub

 

{{out}}

 

=={{header|Vlang}}==

mut s := ""

 

// check that a string is not empty, any of:

s != ""

if s.len() == 0 {

println("empty")

// check that a string is not empty.

test(str2) // prt not empty

 

=={{header|Wee Basic}}==

if string$=""

print 1 "The string is empty."

print 1 "The string is not empty."

endif

 

=={{header|Wren}}==

 

var s = ""

var t = "0"

System.print("'s' is empty? %(isEmpty.call(s))")

 

{{out}}

=={{header|X86-64 Assembly}}==

===UASM 2.52===

option casemap:none

 

main endp

end

{{out}}

<pre>

=={{header|XLISP}}==

<code>STRING-NULL?</code> returns true if its argument is a string of length zero. In a REPL:

 

MY-EMPTY-STRING

[3] (string-null? "A non-empty string")

 

 

=={{header|XPL0}}==

string 0; \use zero-terminated convention, instead of MSb set

char S;

if S(0) # 0 then Text(0, "not empty

");

 

=={{header|Z80 Assembly}}==

{{trans|6502 Assembly}}

An empty string is just a null terminator with no text in front.

 

Checking if a string is empty is simple, just count the number of characters before you reach the terminator. If that count equals zero, the string is empty. Otherwise, the string is not empty.

 

 

GetStringLength:

or a ;compare A to zero (effectively comparing B to zero)

jr z,StringIsEmpty

 

=={{header|zkl}}==

s.toBool() //-->False

 

=={{header|Zoomscript}}==

For typing:

string = ""

if eq string ""

else

print "The string is not empty."

For importing:

 

 

=={{header|Zig}}==

 

pub fn main() !void {

std.debug.print("string empty\n", .{});

}

 

{{omit from|GUISS}}