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45 lines
1.5 KiB
Racket
45 lines
1.5 KiB
Racket
9 years ago
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#lang racket/base
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(require (for-syntax racket/base racket/syntax) racket/contract "../define.rkt" "base.rkt")
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(define-syntax-rule (make-blame-handler try-proc expected-sym)
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(λ(b)
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(λ(x)
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(with-handlers ([exn:fail? (λ(e)
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(raise-blame-error
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b x
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'(expected: "~a" given: "~e")
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expected-sym x))])
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(try-proc x)))))
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(provide+safe make-coercion-contract)
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(define-syntax (make-coercion-contract stx)
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(syntax-case stx ()
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[(_ stem coerce-proc)
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(with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)]
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[can-be-stem? (format-id stx "can-be-~a?" #'stem)])
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#'(make-contract
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#:name 'coerce/stem?
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#:projection (make-blame-handler coerce-proc 'can-be-stem?)))]
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[(_ stem)
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(with-syntax ([->stem (format-id stx "->~a" #'stem)])
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#'(make-coercion-contract stem ->stem))]))
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(define-syntax (define+provide-coercion-contract stx)
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(syntax-case stx ()
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[(_ stem)
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(with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)])
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#'(begin
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(provide+safe coerce/stem?)
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(define coerce/stem? (make-coercion-contract stem))))]))
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(define+provide-coercion-contract int)
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(define+provide-coercion-contract string)
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(define+provide-coercion-contract symbol)
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(define+provide-coercion-contract path)
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(define+provide-coercion-contract boolean)
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(define+provide-coercion-contract list)
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