mirror of
https://github.com/ashinn/chibi-scheme.git
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3ee50bd0d7
It still accepts cyclic lists and returns #f, like SRFI-1 length+. It's convenient to be able to accept improper lists (e.g. for parameter lists), so the old behavior is available as length*. Fixes issue #97.
23 lines
868 B
Scheme
23 lines
868 B
Scheme
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(define-library (srfi 16)
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(export case-lambda)
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(import (scheme))
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(begin
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(define-syntax %case
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(syntax-rules ()
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((%case args len n p ((params ...) . body) . rest)
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(if (= len (length '(params ...)))
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(apply (lambda (params ...) . body) args)
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(%case args len 0 () . rest)))
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((%case args len n (p ...) ((x . y) . body) . rest)
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(%case args len (+ n 1) (p ... x) (y . body) . rest))
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((%case args len n (p ...) (y . body) . rest)
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(if (>= len n)
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(apply (lambda (p ... . y) . body) args)
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(%case args len 0 () . rest)))
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((%case args len n p)
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(error "case-lambda: no cases matched"))))
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(define-syntax case-lambda
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(syntax-rules ()
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((case-lambda . clauses)
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(lambda args (let ((len (length* args))) (%case args len 0 () . clauses))))))))
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