73 lines
2.9 KiB
Scheme
73 lines
2.9 KiB
Scheme
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; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees. See file COPYING.
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; define-enumeration macro
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(define-syntax define-enumeration
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(lambda (form rename compare)
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(let ((name (cadr form))
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(components (list->vector (caddr form)))
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(conc (lambda things
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(string->symbol (apply string-append
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(map (lambda (thing)
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(if (symbol? thing)
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(symbol->string thing)
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thing))
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things)))))
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(%define (rename 'define))
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(%define-syntax (rename 'define-syntax))
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(%begin (rename 'begin))
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(%quote (rename 'quote)))
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(let ((e-name (conc name '- 'enumeration))
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(count (vector-length components)))
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`(,%begin (,%define-syntax ,name
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(cons (let ((components ',components))
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(lambda (e r c)
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(let ((key (cadr e)))
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(cond ((c key 'components)
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(r ',e-name))
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((c key 'enum)
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(let ((which (caddr e)))
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(let loop ((i 0)) ;vector-posq
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(if (< i ,count)
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(if (c which (vector-ref components i))
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i
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(loop (+ i 1)))
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;; (syntax-error "unknown enumerand name"
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;; `(,(cadr e) ,(car e) ,(caddr e)))
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e))))
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(else e)))))
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'(,e-name))) ;Auxiliary binding
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(,%define ,e-name ',components)
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(,%define ,(conc name '- 'count) ,count)))))
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(begin define define-syntax quote))
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(define-syntax components
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(cons (lambda (e r c) `(,(cadr e) components))
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'()))
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(define-syntax enum
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(cons (lambda (e r c) `(,(cadr e) enum ,(caddr e)))
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'()))
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(define-syntax enumerand->name
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(syntax-rules ()
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((enumerand->name ?enumerand ?type)
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(vector-ref (components ?type) ?enumerand))))
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(define-syntax name->enumerand
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(syntax-rules ()
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((name->enumerand ?name ?type)
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(lookup-enumerand (components ?type) ?name))))
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(define (lookup-enumerand components name)
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(let ((len (vector-length components)))
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(let loop ((i 0)) ;vector-posq
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(if (>= i len)
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#f
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(if (eq? name (vector-ref components i))
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i
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(loop (+ i 1)))))))
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