cond ( assoc -- )
Factor handbook > The language > Combinators > Conditional combinators

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Vocabulary
combinators

Inputs and outputs
assoca sequence of quotation pairs and an optional quotation


Word description
Calls the second quotation in the first pair whose first quotation yields a true value. A single quotation will always yield a true value.

The following two phrases are equivalent:
{ { [ X ] [ Y ] } { [ Z ] [ T ] } } cond

X [ Y ] [ Z [ T ] [ no-cond ] if ] if


Errors
Throws a no-cond error if none of the test quotations yield a true value.

Examples
USING: combinators io kernel math ; 0 { { [ dup 0 > ] [ drop "positive" ] } { [ dup 0 < ] [ drop "negative" ] } [ drop "zero" ] } cond print
zero


Definition