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sugar/coerce.rkt

91 lines
2.4 KiB
Racket

#lang racket/base
(require racket/contract net/url xml racket/set)
(module+ test (require rackunit))
(require "len.rkt")
11 years ago
(provide ->int ->string ->list ->boolean ->symbol ->path)
;; general way of coercing to integer
(define/contract (->int x)
(any/c . -> . integer?)
(cond
[(integer? x) x]
[(real? x) (floor x)]
[(and (string? x) (> (len x) 0)) (->int (string->number x))]
[(symbol? x) (->int (->string x))]
[(char? x) (char->integer x)]
[else (or (len x) (error "Can't convert to integer:" x))])) ; try len before giving up
;; general way of coercing to string
(define/contract (->string x)
(any/c . -> . string?)
(cond
[(string? x) x]
[(equal? '() x) ""]
[(symbol? x) (symbol->string x)]
[(number? x) (number->string x)]
[(url? x) (->string (->path x))] ; todo: a url is more than just a path-string ... it has character encoding issues
[(path? x) (path->string x)]
[(char? x) (format "~a" x)]
[(xexpr? x) (xexpr->string x)] ; put this last so other xexprish things don't get caught
[else (error (format "Can't make ~a into string" x))]))
;; general way of coercing to symbol
(define (->symbol thing)
; todo: on bad input, it will pop a string error rather than symbol error
(string->symbol (->string thing)))
;; general way of coercing to path
(define/contract (->path thing)
(any/c . -> . path?)
; todo: on bad input, it will pop a string error rather than path error
(cond
[(url? thing) (apply build-path (map path/param-path (url-path thing)))]
[else (string->path (->string thing))]))
;; general way of coercing to url
(define/contract (->url thing)
(any/c . -> . url?)
; todo: on bad input, it will pop a string error rather than url error
(string->url (->string thing)))
(define (->complete-path thing)
(path->complete-path (->path thing)))
;; general way of coercing to a list
(define/contract (->list x)
(any/c . -> . list?)
(cond
[(list? x) x]
[(vector? x) (vector->list x)]
[(set? x) (set->list x)]
[else (list x)]))
;; general way of coercing to vector
(define (->vector x)
(any/c . -> . vector?)
; todo: on bad input, it will pop a list error rather than vector error
(cond
[(vector? x) x]
[else (list->vector (->list x))]))
;; general way of coercing to boolean
(define/contract (->boolean x)
(any/c . -> . boolean?)
;; in Racket, everything but #f is true
(if x #t #f))