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sugar/unstable/len.rkt

30 lines
1.1 KiB
Racket

#lang racket/base
(require "../define.rkt" racket/sequence)
(define+provide+safe (len x)
((or/c list? vector? sequence? string? symbol? path? hash?) . -> . integer?)
(cond
[(list? x) (length x)]
[(string? x) (string-length x)]
[(symbol? x) (len (symbol->string x))]
[(path? x) (len (path->string x))]
[(vector? x) (vector-length x)]
[(hash? x) (len (hash-keys x))]
[(and (sequence? x) (not (integer? x))) (len (sequence->list x))]
[else (error "len: can't calculate length of" x)]))
(module+ test
(require rackunit racket/set)
(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 (set 1 2 3)) 3)
(check-not-equal? (len (set 1 2)) 3) ; len 2
(check-equal? (len (make-hash '((a . 1) (b . 2) (c . 3)))) 3)
(check-not-equal? (len (make-hash '((a . 1) (b . 2)))) 3)) ; len 2