38 lines
1.2 KiB
Scheme
38 lines
1.2 KiB
Scheme
; Copyright (c) 2003 RT Happe <rthappe at web de>
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; See the file COPYING distributed with the Scheme Untergrund Library
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; See README for documentation.
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(define-syntax assert
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(syntax-rules ()
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((assert ?x ?y0 ...)
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(if (not ?x) (error "Assertion failed" '?x ?y0 ...))) ))
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;; RECEIVE/NAME is a multiple values analogue of named LET.
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(define-syntax receive/name
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(syntax-rules ()
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((_ ?tag ?tuple ?call ?body0 ?body1 ...)
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(letrec ((proc
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(lambda ?tuple
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(let-syntax
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((?tag (syntax-rules ()
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((?tag ?e)
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(call-with-values (lambda () ?e)
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(lambda ?tuple (proc . ?tuple))))
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((?tag . ?args)
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(proc . ?args)))))
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?body0 ?body1 ...))))
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(call-with-values (lambda () ?call) proc)))))
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;; dispatch on type of the first argument
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;; [ should we support a default clause (else ?proc) ? ]
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(define-syntax gen-dispatch
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(syntax-rules ()
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((_ () ?x0 . ?rest)
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#f)
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((_ ((?pred ?proc) ...) ?x0 . ?rest)
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(cond ((?pred ?x0) (?proc ?x0 . ?rest))
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...
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(else (error "unsupported input type" ?x0))))))
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