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41 lines
1.3 KiB
Racket
41 lines
1.3 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base racket/syntax))
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(require racket/contract "../define/provide.rkt" "value.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 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)
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(let ([stem-datum (syntax->datum #'stem)])
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(with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)]
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[->stem (format-id stx "->~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 ->stem 'can-be-stem?))))]))
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(define+provide coerce/int? (make-coercion-contract int))
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(define+provide coerce/symbol? (make-coercion-contract symbol))
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(define+provide coerce/path? (make-coercion-contract path))
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(define+provide coerce/boolean? (make-coercion-contract boolean))
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(define+provide coerce/string? (make-coercion-contract string))
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#|
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(define/contract (foo x)
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(coerce/string? . -> . any/c)
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x)|# |