You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
sugar/coerce.rkt

151 lines
4.2 KiB
Racket

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

#lang racket/base
(require racket/contract net/url xml racket/set)
(module+ test (require rackunit))
(require "len.rkt" "exception.rkt" "define.rkt" "debug.rkt")
(define (make-coercion-error-handler target-format x)
(λ(e) (error (format "Cant convert ~a to ~a" x target-format))))
;; general way of coercing to integer
(define+provide/contract (->int x)
(any/c . -> . integer?)
(try
(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)])
(except [exn:fail? (make-coercion-error-handler 'integer x)])))
;; general way of coercing to string
(define+provide/contract (->string x)
(any/c . -> . string?)
(if (string? x)
x ; fast exit for strings
(try
(cond
[(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)]
[else (error)]) ; put this last so other xexprish things don't get caught
(except [exn:fail? (make-coercion-error-handler 'string x)]))))
;; general way of coercing to html
(define+provide/contract (->html x)
(any/c . -> . string?)
;; todo: omit 'script and 'style tags (and ... ?)
(try (xexpr->string x)
(except [exn:fail? (make-coercion-error-handler 'html x)])))
; must get this right — no escaped chars
;(->html '(script ((type "text/javascript")) "3 > 2"))
;; general way of coercing to symbol
(define+provide/contract (->symbol x)
(any/c . -> . symbol?)
(try (string->symbol (->string x))
(except [exn:fail? (make-coercion-error-handler 'symbol x)])))
;; general way of coercing to path
(define+provide/contract (->path x)
(any/c . -> . path?)
(try
(cond
[(url? x) (apply build-path (map path/param-path (url-path x)))]
[else (string->path (->string x))])
(except [exn:fail? (make-coercion-error-handler 'path x)])))
;; general way of coercing to url
(define+provide/contract (->url x)
(any/c . -> . url?)
(try (string->url (->string x))
(except [exn:fail? (make-coercion-error-handler 'url x)])))
(define+provide/contract (->complete-path x)
(any/c . -> . complete-path?)
(try (path->complete-path (->path x))
(except [exn:fail? (make-coercion-error-handler 'complete-path x)])))
;; general way of coercing to a list
(define+provide/contract (->list x)
(any/c . -> . list?)
(try
(cond
[(list? x) x]
[(vector? x) (vector->list x)]
[(set? x) (set->list x)]
[else (list x)])
(except [exn:fail? (make-coercion-error-handler 'list x)])))
;; general way of coercing to vector
(define+provide/contract (->vector x)
(any/c . -> . vector?)
(try
(cond
[(vector? x) x]
[else (list->vector (->list x))])
(except [exn:fail? (make-coercion-error-handler 'vector x)])))
;; general way of coercing to boolean
(define+provide/contract (->boolean x)
(any/c . -> . boolean?)
(if x #t #f))
;;
;; Coercion contracts
;;
(define-syntax-rule (make-blame-handler try-proc expected-sym)
(λ (b)
(λ (x)
(try (try-proc x)
(except [exn:fail? (λ(e)
(raise-blame-error
b x
'(expected: "~a" given: "~e")
expected-sym x))])))))
(define+provide coerce/integer?
(make-contract
#:name 'coerce/integer?
#:projection (make-blame-handler ->int 'can-be-integer?)))
(define+provide coerce/string?
(make-contract
#:name 'coerce/string?
#:projection (make-blame-handler ->string 'can-be-string?)))
(define+provide coerce/symbol?
(make-contract
#:name 'coerce/symbol?
#:projection (make-blame-handler ->symbol 'can-be-symbol?)))
(define+provide coerce/path?
(make-contract
#:name 'coerce/path?
#:projection (make-blame-handler ->path 'can-be-path?)))
(define+provide coerce/boolean?
(make-contract
#:name 'coerce/boolean?
#:projection (make-blame-handler ->boolean 'can-be-boolean?)))