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sugar/coerce/value.rkt

97 lines
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Racket

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#lang racket/base
(require (for-syntax racket/base racket/syntax))
(require net/url xml racket/set)
(require "../len.rkt" "../define/provide.rkt")
(define (make-coercion-error-handler target-format x)
(λ(e) (error (format "Cant convert ~a to ~a" x target-format))))
(define+provide (->int x)
(with-handlers ([exn:fail? (make-coercion-error-handler 'integer x)])
(cond
[(or (integer? x) (real? x)) (inexact->exact (floor x))]
[(and (string? x) (> (len x) 0)) (->int (string->number x))]
[(symbol? x) (->int (->string x))]
[(char? x) (char->integer x)]
[else (len x)])))
(define+provide (->string x)
(if (string? x)
x ; fast exit for strings
(with-handlers ([exn:fail? (make-coercion-error-handler 'string x)])
(cond
[(equal? '() x) ""]
[(symbol? x) (symbol->string x)]
[(number? x) (number->string x)]
[(path? x) (path->string x)]
[(char? x) (format "~a" x)]
[else (error)]))))
(define+provide (->symbol x)
(if (symbol? x)
x
(with-handlers ([exn:fail? (make-coercion-error-handler 'symbol x)])
(string->symbol (->string x)))))
(define+provide (->path x)
(if (path? x)
x
(with-handlers ([exn:fail? (make-coercion-error-handler 'path x)])
(cond
[(url? x) (apply build-path (map path/param-path (url-path x)))]
[else (string->path (->string x))]))))
(define+provide (->url x)
(with-handlers ([exn:fail? (make-coercion-error-handler 'url x)])
(string->url (->string x))))
(define+provide (->complete-path x)
(with-handlers ([exn:fail? (make-coercion-error-handler 'complete-path x)])
(path->complete-path (->path x))))
(define+provide (->list x)
(if (list? x)
x
(with-handlers ([exn:fail? (make-coercion-error-handler 'list x)])
(cond
[(vector? x) (vector->list x)]
[(set? x) (set->list x)]
[else (list x)]))))
(define+provide (->vector x)
(if (vector? x)
x
(with-handlers ([exn:fail? (make-coercion-error-handler 'vector x)])
(list->vector (->list x)))))
(define+provide (->boolean x)
(and x #t))
(define-syntax (make-*ish-predicate stx)
(syntax-case stx ()
[(_ stem)
(with-syntax ([stemish? (format-id stx "~aish?" #'stem)]
[->stem (format-id stx "->~a" #'stem)])
#`(begin
(define+provide (stemish? x)
(with-handlers ([exn:fail? (λ(e) #f)]) (and (->stem x) #t)))))]))
(make-*ish-predicate int)
(make-*ish-predicate string)
(make-*ish-predicate symbol)
(make-*ish-predicate url)
(make-*ish-predicate complete-path)
(make-*ish-predicate path)
;; no point to having list and vector here; they work with everything