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137 lines
3.9 KiB
Racket
137 lines
3.9 KiB
Racket
#lang racket/base
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(require racket/contract net/url xml racket/set)
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(module+ test (require rackunit))
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(require "len.rkt" "exception.rkt" "define.rkt")
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(provide (contract-out
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[->int (any/c . -> . integer?)]
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[->string (any/c . -> . string?)]
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[->symbol (any/c . -> . symbol?)]
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[->path (any/c . -> . path?)]
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[->complete-path (any/c . -> . complete-path?)]
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[->url (any/c . -> . url?)]
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[->list (any/c . -> . list?)]
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[->vector (any/c . -> . vector?)]
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[->boolean (any/c . -> . boolean?)]))
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;; general way of coercing to integer
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(define (->int x)
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(try
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(cond
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[(or (integer? x) (real? x)) (inexact->exact (floor x))]
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[(and (string? x) (> (len x) 0)) (->int (string->number x))]
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[(symbol? x) (->int (->string x))]
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[(char? x) (char->integer x)]
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[else (len x)])
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(except [exn:fail? (λ(e) (error "Can't convert to integer:" x))])))
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;; general way of coercing to string
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(define (->string x)
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(try
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(cond
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[(string? x) x]
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[(equal? '() x) ""]
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[(symbol? x) (symbol->string x)]
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[(number? x) (number->string x)]
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[(url? x) (->string (->path x))] ; todo: a url is more than just a path-string ... it has character encoding issues
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[(path? x) (path->string x)]
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[(char? x) (format "~a" x)]
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[else (error)]) ; put this last so other xexprish things don't get caught
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into string" x)))])))
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;; general way of coercing to symbol
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(define (->symbol x)
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(try (string->symbol (->string x))
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into symbol" x)))])))
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;; general way of coercing to path
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(define (->path x)
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(try
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(cond
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[(url? x) (apply build-path (map path/param-path (url-path x)))]
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[else (string->path (->string x))])
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into path" x)))])))
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;; general way of coercing to url
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(define (->url x)
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(try (string->url (->string x))
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into url" x)))])))
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(define (->complete-path x)
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(try (path->complete-path (->path x))
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into complete-path" x)))])))
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;; general way of coercing to a list
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(define (->list x)
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(try
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(cond
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[(list? x) x]
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[(vector? x) (vector->list x)]
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[(set? x) (set->list x)]
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[else (list x)])
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into list" x)))])))
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;; general way of coercing to vector
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(define (->vector x)
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(try
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(cond
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[(vector? x) x]
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[else (list->vector (->list x))])
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into vector" x)))])))
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;; general way of coercing to boolean
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(define (->boolean x)
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(try
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(if x #t #f)
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(except [exn:fail? (λ(e) (error (format "Can't make ~a into boolean" x)))])))
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;;
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;; Coercion contracts
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;;
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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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(try (try-proc x)
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(except [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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(define/provide coerce/integer?
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(make-contract
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#:name 'coerce/integer?
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#:projection (make-blame-handler ->int 'can-be-integer?)))
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(define/provide coerce/string?
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(make-contract
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#:name 'coerce/string?
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#:projection (make-blame-handler ->string 'can-be-string?)))
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(define/provide coerce/symbol?
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(make-contract
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#:name 'coerce/symbol?
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#:projection (make-blame-handler ->symbol 'can-be-symbol?)))
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(define/provide coerce/path?
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(make-contract
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#:name 'coerce/path?
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#:projection (make-blame-handler ->path 'can-be-path?)))
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(define/provide coerce/boolean?
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(make-contract
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#:name 'coerce/boolean?
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#:projection (make-blame-handler ->boolean 'can-be-boolean?)))
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