cond-case ( assoc -- quot )
Extra combinators

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Vocabulary
combinators.extras

Inputs

assoc

a sequence of quotation pairs and an optional quotation

Outputs
None

Word description
Similar to case, this evaluates an obj according to the first quotation in each pair. If any quotation returns true, calls the second quotation without obj on the stack.

If there is no quotation that returns true, the default case is taken. If the last element of assoc is a quotation, the quotation is called with obj on the stack. Otherwise, a no-cond error is raised.

Examples

USING: combinators.extras io kernel math ; 0 { { [ 0 > ] [ "positive" ] } { [ 0 < ] [ "negative" ] } [ drop "zero" ] } cond-case print
zero

Definition

USING: arrays combinators kernel quotations sequences ;

IN: combinators.extras

MACRO: cond-case ( assoc -- quot )
    [
        dup callable? [
            [ first [ [ dup ] ] dip compose ]
            [ second [ [ drop ] ] dip compose ] bi 2array
        ] unless
    ] map [ cond ] curry ;