25 lines
794 B
Scheme
25 lines
794 B
Scheme
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(define-syntax message-case
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(syntax-rules (else)
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[(_ msg args
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[(msg-name msg-arg* ...) b b* ...] ...
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[else else1 else2 ...])
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(let ([tmsg msg] [targs args])
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(define-syntax match-and-bind
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(syntax-rules ()
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[(__ y () body)
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(if (null? y)
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body
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(error 'message-case "unmatched ~s" (cons tmsg targs)))]
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[(__ y (a a* (... ...)) body)
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(if (pair? y)
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(let ([a (car y)] [d (cdr y)])
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(match-and-bind d (a* (... ...)) body))
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(error 'message-case "unmatched ~s" (cons tmsg targs)))]))
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(case tmsg
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[(msg-name)
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(match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
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[else else1 else2 ...]))]))
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