match-cond ( assoc -- quot )
Pattern matching

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Vocabulary
match

Inputs

assoc

a sequence of pairs

Outputs
None

Word description
Calls the second quotation in the first pair whose first sequence yields a successful match against the top of the stack. The second quotation, when called, has the hashtable returned from the match call bound as the top namespace so the match variables can be used to retrieve the values. A single quotation will always yield a true value. To have a fallthrough match clause use the _ match variable.

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

Examples

USE: match MATCH-VARS: ?value ; { increment 346126 } { { { increment ?value } [ ?value do-something ] } { { decrement ?value } [ ?value do-something-else ] } { _ [ no-match-found ] } } match-cond

See also
match, MATCH-VARS:, replace-patterns, match-replace

Definition

USING: kernel namespaces quotations sequences ;

IN: match

MACRO: match-cond ( assoc -- quot )
    <reversed> dup ?first callable?
    [ unclip ] [ [ no-match-cond ] ] if [
        first2 [ [ dupd match ] curry ] dip
        [ with-variables ] curry rot [ [ or? ] 2dip if ] 2curry
        append
    ] reduce ;