REBOL Document

While - Function Summary


While a condition block is TRUE, evaluates another block.


while cond-block body-block


cond-block - The cond-block argument. (must be: block)

body-block - The body-block argument. (must be: block)


The first block will be executed each time, and if it returns true the second block will be executed. Both blocks can include any number of expressions.

    str: "string"
    while [not tail? str: next str] [
        print ["length of" str "is" length? str]
    length of tring is 5
    length of ring is 4
    length of ing is 3
    length of ng is 2
    length of g is 1

The most common mistake is to forget to provide a block for the first argument (the condition argument).

BREAK can be used to escape from the WHILE loop at any point.


for - Repeats a block over a range of values.
loop - Evaluates a block a specified number of times.
repeat - Evaluates a block a number of times or over a series.
until - Evaluates a block until it is TRUE.

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