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(define-library (csc match)
(export match)
(import (scheme base))
(begin
(define-syntax matches?
(syntax-rules (! _)
((matches? x _) #t)
((matches? x (! bind)) #t)
((matches? x (pattern))
(and (= 1 (length x))
(matches? (car x) pat)))
((matches? x (pattern pattern1 pattern2 ...))
(and (pair? x)
(matches? (car x) pattern)
(matches? (cdr x) (pattern1 pattern2 ...))))
((matches? x lit)
(eqv? lit x))))
(define-syntax bind-pattern
(syntax-rules (! _)
((bind-pattern x '() result1 result2 ...)
(begin result1 result2 ...))
((bind-pattern x _ result1 result2 ...)
(begin result1 result2 ...))
((bind-pattern x (! bind) result1 result2 ...)
(let ((bind x))
result1 result2 ...))
((bind-pattern x (pattern) result1 result2 ...)
(bind-pattern (car x) pattern result1 result2 ...))
((bind-pattern x (pattern pattern1 pattern2 ...) result1 result2 ...)
(bind-pattern (car x) pattern
(bind-pattern (cdr x) (pattern1 pattern2 ...) result1 result2 ...)))
((bind-pattern x lit result1 result2 ...)
(begin result1 result2 ...))))
(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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