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(define-library (csc match)
(export match)
(import (scheme base))
(begin
(define-syntax matches?
(syntax-rules (_ !)
((matches? x _) #t)
((matches? x '())
(null? x))
((matches? x (! constant))
(equal? x constant))
((matches? x (pattern))
(and (= 1 (length x))
(matches? (car x) pattern)))
((matches? x (pattern1 . pattern2))
(and (pair? x)
(matches? (car x) pattern1)
(matches? (cdr x) pattern2)))
((matches? x identifier) #t)))
(define-syntax bind-pattern
(syntax-rules (_ !)
((bind-pattern x _ result result* ...)
(begin result result* ...))
((bind-pattern x '() result result* ...)
(begin result result* ...))
((bind-pattern x (! constant) result result* ...)
(begin result result* ...))
((bind-pattern x (pattern) result result* ...)
(bind-pattern (car x) pattern result result* ...))
((bind-pattern x (pattern1 . pattern2) result result* ...)
(bind-pattern (car x) pattern1
(bind-pattern (cdr x) pattern2 result result* ...)))
((bind-pattern x identifier result result* ...)
(let ((identifier x))
result result* ...))))
(define-syntax match
(syntax-rules ()
((match x (pattern result1 result2 ...))
(if (matches? x pattern)
(bind-pattern x pattern result1 result2 ...)))
((match x (pattern result1 result2 ...) clause1 clause2 ...)
(if (matches? x pattern)
(bind-pattern x pattern result1 result2 ...)
(match x clause1 clause2 ...)))))))
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