28 lines
622 B
Scheme
28 lines
622 B
Scheme
#lang scheme/base
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(provide true false
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boolean=?
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symbol=?)
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(define-syntax-rule (define-constant id val)
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(...
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(define-syntax id
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(syntax-id-rules (set!)
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[(set! id rhs) (set! val rhs)]
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[(id . args) (val . args)]
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[_ val]))))
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(define-constant true #t)
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(define-constant false #f)
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(define (boolean=? x y)
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(unless (and (boolean? x) (boolean? y))
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(raise-type-error 'boolean=? "boolean" (if (boolean? x) 1 0) x y))
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(eq? x y))
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(define (symbol=? x y)
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(unless (and (symbol? x) (symbol? y))
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(raise-type-error 'symbol=? "symbol" (if (symbol? x) 1 0) x y))
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(eq? x y))
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