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42 lines
1.6 KiB
Scheme
42 lines
1.6 KiB
Scheme
21 years ago
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(module actions mzscheme
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(provide (all-defined))
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;; wrap-action: (syntax-object or #f) symbol syntax-object syntax-object -> syntax-object
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(define (wrap-action action result-name ctxt loc)
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(if action
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(let ((parms (datum->syntax-object
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action
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`(start-pos end-pos ,result-name return-without-pos input-port))))
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(datum->syntax-object ctxt
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`(lambda ,parms ,action)
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loc))
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(datum->syntax-object ctxt 'void loc)))
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;; get-special-action: (syntax-object list) symbol 'a -> syntax-object or 'a
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;; Returns the first action from a rule of the form ((which-special) action)
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(define (get-special-action rules which-special none)
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(cond
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((null? rules) none)
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(else
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(syntax-case (car rules) ()
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(((special) act)
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(eq? (syntax-e (syntax special)) which-special)
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(syntax act))
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(_ (get-special-action (cdr rules) which-special none))))))
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;; filter-out-specials: (syntax-object list) (symbol list) -> (syntax-object list)
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;; Returns a list missing all the rules of the form ((special) action)
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;; where special is a symbol in which specials.
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(define (filter-out-specials rules which-specials)
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(cond
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((null? rules) null)
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(else
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(syntax-case (car rules) ()
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(((special) act)
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(memq (syntax-e (syntax special)) which-specials)
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(filter-out-specials (cdr rules) which-specials))
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(_ (cons (car rules) (filter-out-specials (cdr rules) which-specials)))))))
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)
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