72 lines
2.5 KiB
Racket
72 lines
2.5 KiB
Racket
#lang scribble/doc
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@(require scribble/manual
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scribble/eval
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"guide-utils.ss")
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@title[#:tag "strings"]{Strings (Unicode)}
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A @deftech{string} is a fixed-length array of
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@seclink["characters"]{characters}. It prints using doublequotes,
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where doublequote and backslash characters within the string are
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escaped with backslashes. Other common string escapes are supported,
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including @litchar["\\n"] for a linefeed, @litchar["\\r"] for a
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carriage return, octal escapes using @litchar["\\"] followed by up
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to three octal digits, and hexadecimal escapes with @litchar["\\u"]
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(up to four digits). Unprintable characters in a string are normally
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shown with @litchar["\\u"] when the string is printed.
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@refdetails/gory["parse-string"]{the syntax of strings}
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The @scheme[display] procedure directly writes the characters of a
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string to the current output port (see @secref["i/o"]), in contrast
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to the string-constant syntax used to print a string result.
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@examples[
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"Apple"
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(eval:alts #, @schemevalfont{"\u03BB"} "\u03BB")
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(display "Apple")
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(display "a \"quoted\" thing")
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(display "two\nlines")
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(eval:alts (display #, @schemevalfont{"\u03BB"}) (display "\u03BB"))
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]
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A string can be mutable or immutable; strings written directly as
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expressions are immutable, but most other strings are mutable. The
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@scheme[make-string] procedure creates a mutable string given a length
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and optional fill character. The @scheme[string-ref] procedure
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accesses a character from a string (with 0-based indexing); the
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@scheme[string-set!] procedure changes a character in a mutable
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string.
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@examples[
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(string-ref "Apple" 0)
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(define s (make-string 5 #\.))
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s
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(string-set! s 2 #\u03BB)
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s
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]
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String ordering and case operations are generally
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@defterm{locale-independent}; that is, they work the same for all
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users. A few @defterm{locale-dependent} operations are provided that
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allow the way that strings are case-folded and sorted to depend on the
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end-user's locale. If you're sorting strings, for example, use
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@scheme[string<?] or @scheme[string-ci<?] if the sort result should be
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consistent across machines and users, but use @scheme[string-locale<?]
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or @scheme[string-locale-ci<?] if the sort is purely to order strings
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for an end user.
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@examples[
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(string<? "apple" "Banana")
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(string-ci<? "apple" "Banana")
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(string-upcase "Stra\xDFe")
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(parameterize ([current-locale "C"])
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(string-locale-upcase "Stra\xDFe"))
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]
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For working with plain ASCII, working with raw bytes, or
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encoding/decoding Unicode strings as bytes, use
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@seclink["bytestrings"]{byte strings}.
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@refdetails["strings"]{strings and string procedures}
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