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Evaluates a block until it is TRUE.
The until function evaluates a block until the block returns true. It is different from while because it only requires a single block, which also serves as the condition. However, the block is always evaluated at least once.
The general form is:
while [cond] [body]
num: 0 until[ print num num: num + 1 num >= 2 ] 0 1 2
str: "test" until [ print str tail? str: next str ] test est st t
The last value of the block is returned from the until function. Because this is also the termination condition, it will always be non-none non-false, but that can be useful at times.
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