字符串操作是任何一门编程语言中最常用的操作之一,Scheme 也提供了一系列 procudure 来操作字符串。

1、字符串的比较,分别有string=?string>?string<?string>=?string<=?

这与其他语言中对 string 的比较并无不同,比较字符和长度。

例子:

(string=? "mom" "mom") <graphic> #t
(string<? "mom" "mommy") <graphic> #t
(string>? "Dad" "Dad") <graphic> #f
(string=? "Mom and Dad" "mom and dad") <graphic> #f
(string<? "a" "b" "c") <graphic> #t

注意这些比较操作是大小写敏感。相应的,大小写不敏感的版本:

procedure: (string-ci=? string1 string2 string3 ...)
procedure: (string-ci<? string1 string2 string3 ...)
procedure: (string-ci>? string1 string2 string3 ...)
procedure: (string-ci<=? string1 string2 string3 ...)
procedure: (string-ci>=? string1 string2 string3 ...)

2、从字符构造字符串,使用string过程

(string #\a)  => "a"
(string #\a #\b #\c)  => "abc"

注意换行字符是#\newline ,回车字符是#\return

3、重复N个字符构造字符串

(make-string)  => ""
(make-string 4 #\a)  =>"aaaa")

4、字符串长度 string-length

(string-length "") =>0
(string-length "dennis") => 6

5、取第N个字符,相当于java中的charAt

(string-ref "hi there" 0) <graphic> #\h
(string-ref "hi there" 5) <graphic> #\e

6、修改字符串的第N个字符

(string-Setter! "hello" 0 #\H) => "Hello"

7、拷贝字符串

(let ((str "abc"))
  (eq? str (string-copy str)))  => #f
(let ((str "abc"))
  (equal? str (string-copy str)))  => #t

8、拼接字符串,string-append

(string-append) => ""
(string-append "abc" "defg") => "abcdefg"

9、截取子串

(substring "hi there" 0 1) <graphic> "h"
(substring "hi there" 3 6) <graphic> "the"
(substring "hi there" 5 5) <graphic> ""

10、填充字符串

(let ((str (string-copy "sleepy")))
  (string-fill! str #\Z)
  str) <graphic> "ZZZZZZ"

11、与list的相互转换

(string->list "") <graphic> ()
(string->list "abc") <graphic> (#\a #\b #\c)

(list->string '()) <graphic> ""
(list->string '(#\a #\b #\c)) <graphic> "abc"
(list->string
  (map char-upcase
       (string->list "abc"))) <graphic> "ABC"