72 lines
1.7 KiB
Racket
72 lines
1.7 KiB
Racket
#lang scribble/manual
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@(require scribble/eval
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"utils.rkt"
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(for-label unstable/match
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racket/match
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racket/contract
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racket/base))
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@(define the-eval (make-base-eval))
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@(the-eval '(require unstable/match racket/match))
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@title[#:tag "match"]{Match}
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@defmodule[unstable/match]
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@unstable[@author+email["Sam Tobin-Hochstadt" "samth@ccs.neu.edu"]]
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@defform*[[(== val comparator) (== val)]]{
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A @tech[#:doc '(lib "scribblings/reference/reference.scrbl")]{match expander}
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which checks if the matched value is the same as @racket[val] when
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compared by @racket[comparator]. If @racket[comparator] is
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not provided, it defaults to @racket[equal?].
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@examples[#:eval the-eval
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(match (list 1 2 3)
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[(== (list 1 2 3)) 'yes]
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[_ 'no])
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(match (list 1 2 3)
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[(== (list 1 2 3) eq?) 'yes]
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[_ 'no])
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(match (list 1 2 3)
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[(list 1 2 (== 3 =)) 'yes]
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[_ 'no])
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]
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}
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@addition[@author+email["Carl Eastlund" "cce@racket-lang.org"]]
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@defform[(match? val-expr pat ...)]{
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Returns @scheme[#t] if the result of @scheme[val-expr] matches any of
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@scheme[pat], and returns @scheme[#f] otherwise.
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@defexamples[
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#:eval (eval/require 'racket/match 'unstable/match)
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(match? (list 1 2 3)
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(list a b c)
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(vector x y z))
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(match? (vector 1 2 3)
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(list a b c)
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(vector x y z))
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(match? (+ 1 2 3)
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(list a b c)
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(vector x y z))
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]
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}
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@defform[(as ([lhs-id rhs-expr] ...) pat ...)]{
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As a match expander, binds each @scheme[lhs-id] as a pattern variable with the
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result value of @scheme[rhs-expr], and continues matching each subsequent
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@scheme[pat].
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@defexamples[
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#:eval (eval/require 'racket/match 'unstable/match)
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(match (list 1 2 3)
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[(as ([a 0]) (list b c d)) (list a b c d)])
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]
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}
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