摘要：
练一下 Scheme 中 Hash table 的简单用法。#lang racket(define (count-characters astr) (begin (define ht (make-hash)) (map (lambda (c) (hash-set! ht c (+ 1 (hash-ref ht c 0)))) (string->list astr))) ht)(display (count-characters "asdfjghasdfjaskdjhasdfkjhasdf"))#ha... 阅读全文
