30 lines
1.0 KiB
Scheme
30 lines
1.0 KiB
Scheme
(define-library (scheme case-lambda)
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(import (scheme base))
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(define-syntax case-lambda
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(syntax-rules ()
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((case-lambda (params body0 ...) ...)
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(lambda args
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(let ((len (length args)))
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(letrec-syntax
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((cl (syntax-rules ::: ()
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((cl)
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(error "no matching clause"))
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((cl ((p :::) . body) . rest)
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(if (= len (length '(p :::)))
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(apply (lambda (p :::)
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. body)
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args)
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(cl . rest)))
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((cl ((p ::: . tail) . body)
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. rest)
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(if (>= len (length '(p :::)))
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(apply
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(lambda (p ::: . tail)
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. body)
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args)
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(cl . rest))))))
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(cl (params body0 ...) ...)))))))
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(export case-lambda))
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