While - Function Summary

Summary:

While a condition block is TRUE, evaluates another block.

Usage:

while cond-block body-block

Arguments:

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

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

Description:

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.

Related:

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.