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While[test,body]

evaluates test, then body, repetitively, until test first fails to give True.

Details
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Examples  
Basic Examples  
Scope  
Generalizations & Extensions  
Applications  
Properties & Relations  
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While

While[test,body]

evaluates test, then body, repetitively, until test first fails to give True.

Details

  • While[test] does the loop with a null body.
  • If Break[] is generated in the evaluation of body, the While loop exits.
  • Continue[] exits the evaluation of body, and continues the loop.
  • Unless an explicit Return is used, the value returned by While is Null.
  • Note that in an example like i=0;While[i<0,tot+=f[i];i++] the roles of ; and , are reversed relative to C-like programming languages.

Examples

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Basic Examples  (1)

Print and increment n while the condition n<4 is satisfied:

Wolfram Language code: n = 1;While[n < 4, Print[n];n++]

Scope  (2)

The body can be included as part of the test:

Wolfram Language code: n = 1;While[++n < 4];n
Wolfram Language code: n = 1;While[n < 4, n++];n

Break breaks out of the While:

Wolfram Language code: n = 1;While[True, If[n > 10, Break[]];n++]
Wolfram Language code: n

Generalizations & Extensions  (1)

Test the condition during or at the end of the loop:

Wolfram Language code: While[True, n = Input["enter an integer"]; If[!IntegerQ[n] || n ≤ 0, Break[]]; Print[n, "=", FactorInteger[n]] ]

Applications  (2)

Compute the GCD of two numbers:

Wolfram Language code: {a, b} = {27, 6}; While[b ≠ 0, {a, b} = {b, Mod[a, b]}]; a

Count the number of iterations in a fixed-point calculation:

Wolfram Language code: x = 1.0;i = 0; While[Cos[x] ≠ x, x = Cos[x];i++];{x, i}

Properties & Relations  (4)

If the test is False, the body is never evaluated:

Wolfram Language code: While[False, Print[x]]

While returns Null:

Wolfram Language code: FullForm[n = 1;While[n < 5, n++]]

Use Print to see the iterations:

Wolfram Language code: n = 17;While[(n = Floor[n / 2]) != 0, Print[n]];n

Do iterates a fixed number of times:

Wolfram Language code: x = 1.0; Do[x = (x + 2 / x) / 2, {5}];x

NestWhile is a functional form of While:

Wolfram Language code: NestWhile[Floor[# / 2]&, 10, # > 0&]
Wolfram Language code: x = 10;While[x > 0, x = Floor[x / 2]];x
Wolfram Research (1988), While, Wolfram Language function, https://reference.wolfram.com/language/ref/While.html.

Text

Wolfram Research (1988), While, Wolfram Language function, https://reference.wolfram.com/language/ref/While.html.

CMS

Wolfram Language. 1988. "While." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/While.html.

APA

Wolfram Language. (1988). While. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/While.html

BibTeX

@misc{reference.wolfram_2026_while, author="Wolfram Research", title="{While}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/While.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_while, organization={Wolfram Research}, title={While}, year={1988}, url={https://reference.wolfram.com/language/ref/While.html}, note=[Accessed: 12-June-2026]}