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sugar/len.rkt

15 lines
567 B
Racket

#lang racket/base
(require "define.rkt" racket/set racket/sequence)
(define+provide+safe (len x)
((or/c list? vector? set? 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))]
[(set? x) (len (set->list x))]
[(and (sequence? x) (not (integer? x))) (len (sequence->list x))]
[else (error "len: can't calculate length of" x)]))