(string-ref str k) → char? ;通过下标获取字符串元素
str : string?
k : exact-nonnegative-integer?</pre>
>(string-ref "hello" 0)
#\h
(make-string k [char]) → string?
k : exact-nonnegative-integer?
char : char? = #\nul
通过给定一个字符串长度，和一个默认填充字符串，返回一个可改变的字符串
>(define s (make-string 5 #\z))
>s
"zzzzz"
(string-set! str k char) → void?
str : (and/c string? (not/c immutable?))
k : exact-nonnegative-integer?
char : char?
修改可变字符串str的第k个字符串为char</pre>
>(string-set! s 2 #\&)
>s
"zz&zz"
(string<? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
字符串比较，如果str1<str2 ...+,刚返回#t,
(string<=? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
(string=? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
判断str1,str2 ...+是否相等
(string>? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?</pre>
(string-copy! dest ;目标字符串
dest-start ;目标字符串起始下标
src ;源字符串
[src-start ;源字符串起始下标
src-end]) → void? ;源字符串结束下标
dest : (and/c string? (not/c immutable?))
dest-start : exact-nonnegative-integer?
src : string?
src-start : exact-nonnegative-integer? = 0
src-end : exact-nonnegative-integer? = (string-length src)
>(string-copy! s 0 "hello" 0 5)
>s
"hello"
(string-fill! dest char) → void?
dest : (and/c string? (not/c immutable?))
char : char?
填充字符串</pre>
>(string-fill! s #\q)
>s
"qqqqq"
(string-append str ...) → string?
str : string?
返回一个新的拼接的字符串</pre>
>(string-append "Apple" "Banana")
"AppleBanana"
(string-length str) → exact-nonnegative-integer?
str : string?
返回字符串长度</pre>
>(string-length "Hello")
5
(substring str start [end]) → string?
str : string?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer? = (string-length str)
获取子字符串</pre>
>(substring "hello" 0 4)
"hell"
(string->list str) → (listof char?)
str : string?
将字符串转换为列表</pre>
>(string->list "Apple")
'(#\A #\p #\p #\l #\e)
(list->string lst) → string?
lst : (listof char?)
将列表转换为string</pre>
>(list->string (list #\A #\p #\p #\l #\e))
"Apple"
(build-string n proc) → string?
n : exact-nonnegative-integer?
proc : (exact-nonnegative-integer? . ->. char?)
通过proc以0-n的顺序创建一个长度为n的字符串</pre>
>(build-string 5 (lambda (i) (integer->char (+ i 97))))
"abcde"
(string-ci=? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
当参数str1,str2 ...+经过函数string-foldcase处理，若str1,str2 ...+相等则返回true
(string-ci<? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
(string-ci<=? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?
(string-ci>? str1 str2 ...+) → boolean?
str1 : string?
str2 : string?</pre>
>(string-ci=? "Apple" "apple")
#t
(string-upcase str) → string?
str : string?
将字符串转换为大写
(string-downcase string) → string?
string : string?
将字符串转换为小写
(string-titlecase string) → string?
string : string?
将单词的第一个字母进行大写
(string-foldcase string) → string?
string : string?
将字符串转换为小写，特殊字符存在某种转换</pre>
>(string-foldcase "Straße")
"strasse"
>(string-downcase "Straße")
"straße"
(string-join strs ;以指定分隔符连接字符串
[sep
#:before-first before-first
#:before-last before-last
#:after-last after-last]) → string?
strs : (listof string?)
sep : string? = " "
before-first : string? = ""
before-last : string? = sep
after-last : string? = "")
>(string-join '("one" "two" "three" "four") ";")
"one;two;three;four"
(string-split str ;切分字符串，返回一个列表
[sep
#:trim? trim?
#:repeat? repeat?]) → (listof string?)
str : string?
sep : (or/c string? regexp?) = #px"\\s+"
trim? : any/c = #t
repeat? : any/c = #f)</pre>
>(string-split " foo bar baz \r\n\t")
'("foo" "bar" "baz")
(string-trim str ;去掉字符串前后的sep
[sep
#:left? left?
#:right? right?
#:repeat? repeat?]) → string?
str : string?
sep : (or/c string? regexp?) = #px"\\s+"
left? : any/c = #t
right? : any/c = #t repeat? : any/c = #f</pre>
>(string-trim " foo bar baz \r\n\t")
"foo bar baz"
(non-empty-string? x) → boolean?
x : any/c
当x是字符串且不为空时，返回#t，否则返回#f</pre>
>(non-empty-string? "")
#f
(string-contains? s contained) → boolean?
s : string?
contained : string?
判断containde是否存在于s中</pre>
>(string-contains? "ab" "a")
#t
(string-prefix? s prefix) → boolean?
s : string?
prefix : string?
判断是否是开头
(string-suffix? s suffix) → boolean?
s : string?
suffix : string?
判断是否是结尾</pre>
>(string-prefix? "hello" "he")
#t
>(string-suffix? "hello" "lo")
#t
Ref： 1.官方文档