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Until

Until[test,body]

evaluates body and then test, repetitively, until test first gives True.

Details

Until[test] evaluates test repeatedly, effectively with a null body.
If Break[] is generated in the evaluation of body, the Until loop exits.
Continue[] exits the evaluation of body and continues the loop.
Unless an explicit Return is used, the value returned by Until is Null.
Note that in an example like i=0;Until[i>10,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 until the condition n>3 is satisfied:

Scope (1)

Break breaks out of the Until loop:

Applications (2)

Compute the GCD of two numbers:

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

Properties & Relations (2)

Until[test,body] evaluates body before test:

While[test,body] evaluates test before body:

Until and While require opposite tests to reproduce similar behavior:

However, the test is evaluated one more time in the While loop:

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