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pollen/readability.rkt

63 lines
1.8 KiB
Racket

#lang racket/base
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(require racket/contract)
(require (only-in racket/list empty?))
(require (only-in racket/format ~a))
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(module+ test (require rackunit))
(provide (all-defined-out))
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;; general way of coercing to string
(define/contract (as-string x)
(any/c . -> . string?)
(cond
[(empty? x) ""]
[(symbol? x) (symbol->string x)]
[(number? x) (number->string x)]
[(path? x) (path->string x)]
[(char? x) (~a x)]
[else (error (format "Can't make ~a into string" x))]))
(module+ test
(check-equal? (as-string '()) "")
(check-equal? (as-string 'foo) "foo")
(check-equal? (as-string 123) "123")
(define file-name-as-text "foo.txt")
(check-equal? (as-string (string->path file-name-as-text)) file-name-as-text)
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(check-equal? (as-string #\¶) ""))
;; general way of coercing to a list
(define (as-list x)
(any/c . -> . list?)
(cond
[(list? x) x]
[(vector? x) (vector->list x)]
[else (list x)]))
(module+ test
(check-equal? (as-list '(1 2 3)) '(1 2 3))
(check-equal? (as-list (list->vector '(1 2 3))) '(1 2 3))
(check-equal? (as-list "foo") (list "foo")))
;; general way of asking for length
(define (len x)
(any/c . -> . integer?)
(cond
[(list? x) (length x)]
[(string? x) (string-length x)]
[(symbol? x) (len (as-string x))]
[(vector? x) (vector-length x)]
[(hash? x) (len (hash-keys x))]
[else #f]))
(module+ test
(check-equal? (len '(1 2 3)) 3)
(check-not-equal? (len '(1 2)) 3) ; len 2
(check-equal? (len "foo") 3)
(check-not-equal? (len "fo") 3) ; len 2
(check-equal? (len 'foo) 3)
(check-not-equal? (len 'fo) 3) ; len 2
(check-equal? (len (list->vector '(1 2 3))) 3)
(check-not-equal? (len (list->vector '(1 2))) 3) ; len 2
(check-equal? (len (make-hash '((a 1) (b 2) (c 3)))) 3)
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(check-not-equal? (len (make-hash '((a 1) (b 2) (b 3)))) 3)) ; len 2