27 mzlib/match

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On this page:

match
match-lambda
match-lambda*
match-let
match-let*
match-letrec
match-define
define-match-expander
match-equality-test

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( require mzlib/match)

The mzlib/match library provides a match form similar to that of scheme/match, but with an different (older and less extensible) syntax of patterns.

( match val-expr clause ...)

clause |  | = |  | [pat expr ...+]
|  | | |  | [pat (=> id) expr ...+]

See match from scheme/match for a description of matching. The grammar of pat for this match is as follows:

pat |  | ::= |  | id |  | match anything, bind identifier
|  | | |  | _ |  | match anything
|  | | |  | literal |  | match literal
|  | | |  | 'datum |  | match equal? datum
|  | | |  | (lvp ...) |  | match sequence of lvps
|  | | |  | (lvp ... . pat) |  | match lvps consed onto a pat
|  | | |  | #(lvp ...) |  | match vector of pats
|  | | |  | #&pat |  | match boxed pat
|  | | |  | ($ struct-id pat ...) |  | match struct-id instance
|  | | |  | (and pat ...) |  | match when all pats match
|  | | |  | (or pat ...) |  | match when any pat match
|  | | |  | (not pat ...) |  | match when no pat match
|  | | |  | (= expr pat) |  | match (expr value) to pat
|  | | |  | (? pred-expr pat ...) |  | match if (expr value) and pats
|  | | |  | `qp |  | match quasipattern
literal |  | ::= |  | #t |  | match true
|  | | |  | #f |  | match false
|  | | |  | string |  | match equal? string
|  | | |  | number |  | match equal? number
|  | | |  | character |  | match equal? character
|  | | |  | bytes |  | match equal? byte string
|  | | |  | keyword |  | match equal? keyword
|  | | |  | regexp |  | match equal? regexp literal
|  | | |  | pregexp |  | match equal? pregexp literal
lvp |  | ::= |  | pat |  | greedily match pat instances
|  | | |  | pat |  | match pat
ooo |  | ::= |  | ... |  | zero or more; ... is literal
|  | | |  | ___ |  | zero or more
|  | | |  | ..k |  | k or more
|  | | |  | __k |  | k or more
qp |  | ::= |  | literal |  | match literal
|  | | |  | id |  | match equal? symbol
|  | | |  | (qp ...) |  | match sequences of qps
|  | | |  | (qp ... . qp) |  | match sequence of qps consed onto a qp
|  | | |  | (qp ... qp ooo) |  | match qps consed onto a repeated qp
|  | | |  | #(qp ...) |  | match vector of qps
|  | | |  | #&qp |  | match boxed qp
|  | | |  | ,pat |  | match pat
|  | | |  | ,@pat |  | match pat, spliced

( match-lambda clause ...)

( match-lambda* clause ...)

( match-let ([pat expr] ...) body ...+)

( match-let* ([pat expr] ...) body ...+)

( match-letrec ([pat expr] ...) body ...+)

( match-define pat expr)

Analogous to the combined forms from scheme/match.

( define-match-expander id proc-expr)
( define-match-expander id proc-expr proc-expr)
( define-match-expander id proc-expr proc-expr proc-expr)

( match-equality-test) → (any/c any/c . -> . any)
( match-equality-test comp-proc) → void?
comp-proc : (any/c any/c . -> . any)

Analogous to the form and parameter from scheme/match. The define-match-expander form, however, supports an extra proc-expr as the middle one: an expander for use with match from mzlib/match.
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