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