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r6rs-lib
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<a name="node_chap_1"></a>
<h1 class=chapter>
<div class=chapterheading><a href="r6rs-lib-Z-H-1.html#node_toc_node_chap_1">Chapter 1</a></div><br>
<a href="r6rs-lib-Z-H-1.html#node_toc_node_chap_1">Unicode</a></h1>
<p></p>
<p>
</p>
<p>
The procedures exported by the <tt>(rnrs unicode (6))</tt><a name="node_idx_2"></a>library provide access to some aspects
of the Unicode semantics for characters and strings:
category information, case-independent comparisons,
case mappings, and normalization [<a href="r6rs-lib-Z-H-21.html#node_bib_12">12</a>].</p>
<p>
Some of the procedures that operate on characters or strings ignore the
difference between upper case and lower case. These procedures
have “<tt>-ci</tt>” (for “case
insensitive”) embedded in their names.</p>
<p>
</p>
<a name="node_sec_1.1"></a>
<h2 class=section><a href="r6rs-lib-Z-H-1.html#node_toc_node_sec_1.1">1.1 Characters</a></h2>
<p></p>
<p></p>
<div align=left><tt>(<a name="node_idx_4"></a>char-upcase<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_6"></a>char-downcase<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_8"></a>char-titlecase<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_10"></a>char-foldcase<i> char</i>)</tt> procedure </div>
<p>
These procedures take a character argument and return a character
result. If the argument is an upper-case or title-case character, and if
there is a single character that is its lower-case form, then
<tt>char-downcase</tt> returns that character. If the argument is a lower-case
or title-case character, and there is a single character that is
its upper-case form, then <tt>char-upcase</tt> returns that character.
If the argument is a lower-case
or upper-case character, and there is a single character that is
its title-case form, then <tt>char-titlecase</tt> returns that character.
If the argument is not a title-case character and there is no single
character that is its title-case form, then <tt>char-titlecase</tt>
returns the upper-case form of the argument.
Finally, if the character has a case-folded character,
then <tt>char-foldcase</tt> returns that character.
Otherwise the character returned is the same
as the argument.
For Turkic characters <u>I</u> (<tt>#<tt>\</tt>x130</tt>)
and (<tt>#<tt>\</tt>x131</tt>),
<tt>char-foldcase</tt> behaves as the identity function; otherwise
<tt>char-foldcase</tt> is the
same as <tt>char-downcase</tt> composed with <tt>char-upcase</tt>.</p>
<p>
</p>
<tt>(char-upcase <tt>#</tt><tt>\</tt>i) ⇒ <tt>#</tt><tt>\</tt>I<br>
(char-downcase <tt>#</tt><tt>\</tt>i) ⇒ <tt>#</tt><tt>\</tt>i<br>
(char-titlecase <tt>#</tt><tt>\</tt>i) ⇒ <tt>#</tt><tt>\</tt>I<br>
(char-foldcase <tt>#</tt><tt>\</tt>i) ⇒ <tt>#</tt><tt>\</tt>i<br>
<br>
(char-upcase <tt>#</tt><tt>\</tt>ß) ⇒ <tt>#</tt><tt>\</tt>ß<br>
(char-downcase <tt>#</tt><tt>\</tt>ß) ⇒ <tt>#</tt><tt>\</tt>ß<br>
(char-titlecase <tt>#</tt><tt>\</tt>ß) ⇒ <tt>#</tt><tt>\</tt>ß<br>
(char-foldcase <tt>#</tt><tt>\</tt>ß) ⇒ <tt>#</tt><tt>\</tt>ß<br>
<br>
(char-upcase <tt>#</tt><tt>\</tt>Σ) ⇒ <tt>#</tt><tt>\</tt>Σ<br>
(char-downcase <tt>#</tt><tt>\</tt>Σ) ⇒ <tt>#</tt><tt>\</tt>σ<br>
(char-titlecase <tt>#</tt><tt>\</tt>Σ) ⇒ <tt>#</tt><tt>\</tt>Σ<br>
(char-foldcase <tt>#</tt><tt>\</tt>Σ) ⇒ <tt>#</tt><tt>\</tt>σ<br>
<br>
(char-upcase <tt>#</tt><tt>\</tt>ς) ⇒ <tt>#</tt><tt>\</tt>Σ<br>
(char-downcase <tt>#</tt><tt>\</tt>ς) ⇒ <tt>#</tt><tt>\</tt>ς<br>
(char-titlecase <tt>#</tt><tt>\</tt>ς) ⇒ <tt>#</tt><tt>\</tt>Σ<br>
(char-foldcase <tt>#</tt><tt>\</tt>ς) ⇒ <tt>#</tt><tt>\</tt>σ<br>
<p></tt></p>
<p>
</p>
<blockquote><em>Note: </em>
Note that <tt>char-titlecase</tt> does not always return a title-case
character.
</blockquote><p>
</p>
<blockquote><em>Note: </em>
These procedures are consistent with
Unicode’s locale-independent mappings from scalar values to
scalar values for upcase, downcase, titlecase, and case-folding
operations. These mappings can be extracted from <tt>UnicodeData.txt</tt> and <tt>CaseFolding.txt</tt> from the Unicode
Consortium, ignoring Turkic mappings in the latter.<p>
Note that these character-based procedures are an incomplete
approximation to case conversion, even ignoring the user’s locale.
In general, case mappings require the context of a string, both in
arguments and in result. The <tt>string-upcase</tt>, <tt>string-downcase</tt>, <tt>string-titlecase</tt>, and <tt>string-foldcase</tt> procedures (section <a href="#node_sec_1.2">1.2</a>)
perform more general case conversion.
</p>
</blockquote>
<p></p>
<p>
</p>
<p></p>
<div align=left><tt>(<a name="node_idx_12"></a>char-ci=?<i> <i>char<sub>1</sub></i> <i>char<sub>2</sub></i> <i>char<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_14"></a>char-ci<?<i> <i>char<sub>1</sub></i> <i>char<sub>2</sub></i> <i>char<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_16"></a>char-ci>?<i> <i>char<sub>1</sub></i> <i>char<sub>2</sub></i> <i>char<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_18"></a>char-ci<=?<i> <i>char<sub>1</sub></i> <i>char<sub>2</sub></i> <i>char<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_20"></a>char-ci>=?<i> <i>char<sub>1</sub></i> <i>char<sub>2</sub></i> <i>char<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<p>
These procedures are similar to <tt>char=?</tt>, etc., but operate
on the case-folded versions of the characters.</p>
<p>
</p>
<tt>(char-ci<? <tt>#</tt><tt>\</tt>z <tt>#</tt><tt>\</tt>Z) ⇒ <tt>#f</tt><br>
(char-ci=? <tt>#</tt><tt>\</tt>z <tt>#</tt><tt>\</tt>Z) ⇒ <tt>#t</tt><br>
(char-ci=? <tt>#</tt><tt>\</tt>ς <tt>#</tt><tt>\</tt>σ) ⇒ <tt>#t</tt><p></tt>
</p>
<p></p>
<p>
</p>
<p></p>
<div align=left><tt>(<a name="node_idx_22"></a>char-alphabetic?<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_24"></a>char-numeric?<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_26"></a>char-whitespace?<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_28"></a>char-upper-case?<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_30"></a>char-lower-case?<i> char</i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_32"></a>char-title-case?<i> char</i>)</tt> procedure </div>
<p>
These procedures return <tt>#t</tt> if their arguments are alphabetic,
numeric, whitespace, upper-case, lower-case, or title-case characters,
respectively; otherwise they return <tt>#f</tt>.</p>
<p>
A character is alphabetic if it has the Unicode “Alphabetic”
property. A character is numeric if it has the Unicode “Numeric”
property. A character is whitespace if has the Unicode
“White_Space” property.
A character is upper case if it has the Unicode
“Uppercase” property, lower case if it has the “Lowercase”
property, and title case if it is in the Lt general category.</p>
<p>
</p>
<tt>(char-alphabetic? <tt>#</tt><tt>\</tt>a) ⇒ <tt>#t</tt><br>
(char-numeric? <tt>#</tt><tt>\</tt>1) ⇒ <tt>#t</tt><br>
(char-whitespace? <tt>#</tt><tt>\</tt>space) ⇒ <tt>#t</tt><br>
(char-whitespace? <tt>#</tt><tt>\</tt>x00A0) ⇒ <tt>#t</tt><br>
(char-upper-case? <tt>#</tt><tt>\</tt>Σ) ⇒ <tt>#t</tt><br>
(char-lower-case? <tt>#</tt><tt>\</tt>σ) ⇒ <tt>#t</tt><br>
(char-lower-case? <tt>#</tt><tt>\</tt>x00AA) ⇒ <tt>#t</tt><br>
(char-title-case? <tt>#</tt><tt>\</tt>I) ⇒ <tt>#f</tt><br>
(char-title-case? <tt>#</tt><tt>\</tt>x01C5) ⇒ <tt>#t</tt><p></tt>
</p>
<p></p>
<p>
</p>
<p></p>
<div align=left><tt>(<a name="node_idx_34"></a>char-general-category<i> char</i>)</tt> procedure </div>
<p>
Returns a symbol representing the
Unicode general category of <i>char</i>, one of <tt>Lu</tt>, <tt>Ll</tt>, <tt>Lt</tt>,
<tt>Lm</tt>, <tt>Lo</tt>, <tt>Mn</tt>, <tt>Mc</tt>, <tt>Me</tt>, <tt>Nd</tt>, <tt>Nl</tt>,
<tt>No</tt>, <tt>Ps</tt>, <tt>Pe</tt>, <tt>Pi</tt>, <tt>Pf</tt>, <tt>Pd</tt>, <tt>Pc</tt>,
<tt>Po</tt>, <tt>Sc</tt>, <tt>Sm</tt>, <tt>Sk</tt>, <tt>So</tt>, <tt>Zs</tt>, <tt>Zp</tt>,
<tt>Zl</tt>, <tt>Cc</tt>, <tt>Cf</tt>, <tt>Cs</tt>, <tt>Co</tt>, or <tt>Cn</tt>.</p>
<p>
</p>
<tt>(char-general-category #<tt>\</tt>a) ⇒ Ll<br>
(char-general-category #<tt>\</tt>space) <br> ⇒ Zs<br>
(char-general-category #<tt>\</tt>x10FFFF) <br> ⇒ Cn <br>
<p></tt>
</p>
<p></p>
<p>
</p>
<a name="node_sec_1.2"></a>
<h2 class=section><a href="r6rs-lib-Z-H-1.html#node_toc_node_sec_1.2">1.2 Strings</a></h2>
<p></p>
<p></p>
<div align=left><tt>(<a name="node_idx_36"></a>string-upcase<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_38"></a>string-downcase<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_40"></a>string-titlecase<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_42"></a>string-foldcase<i> <i>string</i></i>)</tt> procedure </div>
<p>
These procedures take a string argument and return a string
result. They are defined in terms of Unicode’s locale-independent
case mappings from Unicode scalar-value sequences to scalar-value sequences.
In particular, the length of the result string can be different from
the length of the input string.
When the specified result is equal in the sense of <tt>string=?</tt> to the
argument, these procedures may return the argument instead of a newly
allocated string.</p>
<p>
The <tt>string-upcase</tt> procedure converts a string to upper case;
<tt>string-downcase</tt> converts a string to lower case. The <tt>string-foldcase</tt> procedure converts the string to its case-folded
counterpart, using the full case-folding mapping, but without the
special mappings for Turkic languages. The <tt>string-titlecase</tt>
procedure converts the first cased character of each word via <tt>char-titlecase</tt>, and downcases all other cased characters.</p>
<p>
</p>
<tt>(string-upcase "Hi") ⇒ "HI"<br>
(string-downcase "Hi") ⇒ "hi"<br>
(string-foldcase "Hi") ⇒ "hi"<br>
<br>
(string-upcase "Straße") ⇒ "STRASSE"<br>
(string-downcase "Straße") ⇒ "straße"<br>
(string-foldcase "Straße") ⇒ "strasse"<br>
(string-downcase "STRASSE") ⇒ "strasse"<br>
<br>
(string-downcase "Σ") ⇒ "σ"<br>
<br>
; Chi Alpha Omicron Sigma:<br>
(string-upcase "<i>XAO</i>Σ") ⇒ "<i>XAO</i>Σ" <br>
(string-downcase "<i>XAO</i>Σ") ⇒ "χα<em>o</em>ς"<br>
(string-downcase "<i>XAO</i>ΣΣ") ⇒ "χα<em>o</em>σς"<br>
(string-downcase "<i>XAO</i>Σ Σ") ⇒ "χα<em>o</em>ς σ"<br>
(string-foldcase "<i>XAO</i>ΣΣ") ⇒ "χα<em>o</em>σσ"<br>
(string-upcase "χα<em>o</em>ς") ⇒ "<i>XAO</i>Σ"<br>
(string-upcase "χα<em>o</em>σ") ⇒ "<i>XAO</i>Σ"<br>
<br>
(string-titlecase "kNock KNoCK")<br>
⇒ "Knock Knock"<br>
(string-titlecase "who’s there?")<br>
⇒ "Who’s There?"<br>
(string-titlecase "r6rs") ⇒ "R6Rs"<br>
(string-titlecase "R6RS") ⇒ "R6Rs"<p></tt></p>
<p>
</p>
<blockquote><em>Note: </em>
The case mappings needed for implementing these procedures
can be extracted from <tt>UnicodeData.txt</tt>, <tt>SpecialCasing.txt</tt>, <tt>WordBreakProperty.txt</tt>
(the “MidLetter” property partly defines case-ignorable characters),
and <tt>CaseFolding.txt</tt> from the Unicode Consortium.<p>
Since these procedures are locale-independent, they may not
be appropriate for some locales.
</p>
</blockquote><p>
</p>
<blockquote><em>Note: </em>
Word breaking, as needed for the correct casing of Σ and for
<tt>string-titlecase</tt>, is specified in Unicode Standard Annex
#29 [<a href="r6rs-lib-Z-H-21.html#node_bib_5">5</a>].
</blockquote><p>
</p>
<p></p>
<p>
</p>
<p></p>
<div align=left><tt>(<a name="node_idx_44"></a>string-ci=?<i> <i>string<sub>1</sub></i> <i>string<sub>2</sub></i> <i>string<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_46"></a>string-ci<?<i> <i>string<sub>1</sub></i> <i>string<sub>2</sub></i> <i>string<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_48"></a>string-ci>?<i> <i>string<sub>1</sub></i> <i>string<sub>2</sub></i> <i>string<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_50"></a>string-ci<=?<i> <i>string<sub>1</sub></i> <i>string<sub>2</sub></i> <i>string<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_52"></a>string-ci>=?<i> <i>string<sub>1</sub></i> <i>string<sub>2</sub></i> <i>string<sub>3</sub></i> <tt>...</tt></i>)</tt> procedure </div>
<p>
These procedures are similar to <tt>string=?</tt>, etc., but
operate on the case-folded versions of the strings.</p>
<p>
</p>
<tt>(string-ci<? "z" "Z") ⇒ <tt>#f</tt><br>
(string-ci=? "z" "Z") ⇒ <tt>#t</tt><br>
(string-ci=? "Straße" "Strasse") <br>
⇒ <tt>#t</tt><br>
(string-ci=? "Straße" "STRASSE")<br>
⇒ <tt>#t</tt><br>
(string-ci=? "<i>XAO</i>Σ" "χα<em>o</em>σ")<br>
⇒ <tt>#t</tt><p></tt></p>
<p>
</p>
<p></p>
<p>
</p>
<p></p>
<div align=left><tt>(<a name="node_idx_54"></a>string-normalize-nfd<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_56"></a>string-normalize-nfkd<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_58"></a>string-normalize-nfc<i> <i>string</i></i>)</tt> procedure </div>
<div align=left><tt>(<a name="node_idx_60"></a>string-normalize-nfkc<i> <i>string</i></i>)</tt> procedure </div>
<p>
These procedures take a string argument and return a string
result, which is the input string normalized
to Unicode normalization form D, KD, C, or KC, respectively.
When the specified result is equal in the sense of <tt>string=?</tt> to the
argument, these procedures may return the argument instead of a newly
allocated string.</p>
<p>
</p>
<tt>(string-normalize-nfd "<tt>\</tt>xE9;")<br>
⇒ "<tt>\</tt>x65;<tt>\</tt>x301;"<br>
(string-normalize-nfc "<tt>\</tt>xE9;")<br>
⇒ "<tt>\</tt>xE9;"<br>
(string-normalize-nfd "<tt>\</tt>x65;<tt>\</tt>x301;")<br>
⇒ "<tt>\</tt>x65;<tt>\</tt>x301;"<br>
(string-normalize-nfc "<tt>\</tt>x65;<tt>\</tt>x301;")<br>
⇒ "<tt>\</tt>xE9;"<p></tt>
</p>
<p></p>
<p>
</p>
<p></p>
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