27 lines
843 B
Scheme
27 lines
843 B
Scheme
(define-library (scheme case-lambda)
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(import (scheme base))
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(define (length+ list)
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(if (pair? list)
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(+ 1 (length+ (cdr list)))
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0))
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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 (formal . body) . rest)
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(if (if (list? 'formal)
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(= len (length 'formal))
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(>= len (length+ 'formal)))
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(apply (lambda formal . body) 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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