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91 lines
2.4 KiB
Racket
91 lines
2.4 KiB
Racket
11 years ago
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#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")
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(provide ->int ->string ->list ->boolean ->symbol)
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;; general way of coercing to integer
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(define/contract (->int x)
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(any/c . -> . integer?)
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(cond
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[(integer? x) x]
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[(real? x) (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 (or (len x) (error "Can't convert to integer:" x))])) ; try len before giving up
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;; general way of coercing to string
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(define/contract (->string x)
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(any/c . -> . string?)
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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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[(xexpr? x) (xexpr->string x)] ; put this last so other xexprish things don't get caught
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[else (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 thing)
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; todo: on bad input, it will pop a string error rather than symbol error
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(string->symbol (->string thing)))
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;; general way of coercing to path
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(define/contract (->path thing)
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(any/c . -> . path?)
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; todo: on bad input, it will pop a string error rather than path error
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(cond
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[(url? thing) (apply build-path (map path/param-path (url-path thing)))]
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[else (string->path (->string thing))]))
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;; general way of coercing to url
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(define/contract (->url thing)
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(any/c . -> . url?)
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; todo: on bad input, it will pop a string error rather than url error
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(string->url (->string thing)))
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(define (->complete-path thing)
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(path->complete-path (->path thing)))
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;; general way of coercing to a list
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(define/contract (->list x)
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(any/c . -> . list?)
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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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;; general way of coercing to vector
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(define (->vector x)
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(any/c . -> . vector?)
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; todo: on bad input, it will pop a list error rather than vector error
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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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;; general way of coercing to boolean
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(define/contract (->boolean x)
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(any/c . -> . boolean?)
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;; in Racket, everything but #f is true
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(if x #t #f))
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