forked from syndicate-lang/marketplace-ssh-2014
36 lines
925 B
Racket
36 lines
925 B
Racket
#lang racket/base
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(provide define-mapping)
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(define-syntax check-defaults
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(syntax-rules ()
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((_ fn bn fd bd #:forward-default new-fd rest ...)
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(check-defaults fn bn new-fd bd rest ...))
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((_ fn bn fd bd #:backward-default new-bd rest ...)
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(check-defaults fn bn fd new-bd rest ...))
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((_ fn bn fd bd (lhs rhs) ...)
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(begin
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(define (fn l)
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(case l
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((lhs) 'rhs) ...
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(else (fd l))))
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(define (bn r)
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(case r
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((rhs) 'lhs) ...
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(else (bd r))))))))
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(define (die-with-mapping-name n)
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(lambda (v)
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(raise (exn:fail:contract
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(format "~v: Mapping not found for ~v" n v)
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(current-continuation-marks)))))
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(define-syntax define-mapping
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(syntax-rules ()
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((_ forward-name backward-name rest ...)
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(check-defaults forward-name
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backward-name
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(die-with-mapping-name 'forward-name)
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(die-with-mapping-name 'backward-name)
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rest ...))))
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