libstdc++-v3/doc/html/manual/locales.html

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   3 <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 14. Locales</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="localization.html" title="Part VI.  Localization" /><link rel="prev" href="localization.html" title="Part VI.  Localization" /><link rel="next" href="facets.html" title="Chapter 15. Facets aka Categories" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 14. Locales</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="localization.html">Prev</a> </td><th width="60%" align="center">Part VI.
   4   Localization
   5
   6 </th><td width="20%" align="right"> <a accesskey="n" href="facets.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 14. Locales"><div class="titlepage"><div><div><h2 class="title"><a id="manual.localization.locales"></a>Chapter 14. Locales</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="locales.html#manual.localization.locales.locale">locale</a></span></dt><dd><dl><dt><span class="sect2"><a href="locales.html#locales.locale.req">Requirements</a></span></dt><dt><span class="sect2"><a href="locales.html#locales.locale.design">Design</a></span></dt><dt><span class="sect2"><a href="locales.html#locales.locale.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="locales.html#locales.locale.future">Future</a></span></dt></dl></dd></dl></div><div class="sect1" title="locale"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.localization.locales.locale"></a>locale</h2></div></div></div><p>
   7 Describes the basic locale object, including nested
   8 classes id, facet, and the reference-counted implementation object,
   9 class _Impl.
  10 </p><div class="sect2" title="Requirements"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.req"></a>Requirements</h3></div></div></div><p>
  11 Class locale is non-templatized and has two distinct types nested
  12 inside of it:
  13 </p><div class="blockquote"><blockquote class="blockquote"><p>
  14 <span class="emphasis"><em>
  15 class facet
  16 22.1.1.1.2 Class locale::facet
  17 </em></span>
  18 </p></blockquote></div><p>
  19 Facets actually implement locale functionality. For instance, a facet
  20 called numpunct is the data objects that can be used to query for the
  21 thousands separator is in the German locale.
  22 </p><p>
  23 Literally, a facet is strictly defined:
  24 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  25       Containing the following public data member:
  26     </p><p>
  27       <code class="code">static locale::id id;</code>
  28     </p></li><li class="listitem"><p>
  29       Derived from another facet:
  30     </p><p>
  31       <code class="code">class gnu_codecvt: public std::ctype&lt;user-defined-type&gt;</code>
  32     </p></li></ul></div><p>
  33 Of interest in this class are the memory management options explicitly
  34 specified as an argument to facet's constructor. Each constructor of a
  35 facet class takes a std::size_t __refs argument: if __refs == 0, the
  36 facet is deleted when the locale containing it is destroyed. If __refs
  37 == 1, the facet is not destroyed, even when it is no longer
  38 referenced.
  39 </p><div class="blockquote"><blockquote class="blockquote"><p>
  40 <span class="emphasis"><em>
  41 class id
  42 22.1.1.1.3 - Class locale::id
  43 </em></span>
  44 </p></blockquote></div><p>
  45 Provides an index for looking up specific facets.
  46 </p></div><div class="sect2" title="Design"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.design"></a>Design</h3></div></div></div><p>
  47 The major design challenge is fitting an object-orientated and
  48 non-global locale design on top of POSIX and other relevant standards,
  49 which include the Single Unix (nee X/Open.)
  50 </p><p>
  51 Because C and earlier versions of POSIX fall down so completely,
  52 portability is an issue.
  53 </p></div><div class="sect2" title="Implementation"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.impl"></a>Implementation</h3></div></div></div><div class="sect3" title="Interacting with &quot;C&quot; locales"><div class="titlepage"><div><div><h4 class="title"><a id="locale.impl.c"></a>Interacting with "C" locales</h4></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  54        <code class="code">`locale -a`</code> displays available locales.
  55      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
  56 af_ZA
  57 ar_AE
  58 ar_AE.utf8
  59 ar_BH
  60 ar_BH.utf8
  61 ar_DZ
  62 ar_DZ.utf8
  63 ar_EG
  64 ar_EG.utf8
  65 ar_IN
  66 ar_IQ
  67 ar_IQ.utf8
  68 ar_JO
  69 ar_JO.utf8
  70 ar_KW
  71 ar_KW.utf8
  72 ar_LB
  73 ar_LB.utf8
  74 ar_LY
  75 ar_LY.utf8
  76 ar_MA
  77 ar_MA.utf8
  78 ar_OM
  79 ar_OM.utf8
  80 ar_QA
  81 ar_QA.utf8
  82 ar_SA
  83 ar_SA.utf8
  84 ar_SD
  85 ar_SD.utf8
  86 ar_SY
  87 ar_SY.utf8
  88 ar_TN
  89 ar_TN.utf8
  90 ar_YE
  91 ar_YE.utf8
  92 be_BY
  93 be_BY.utf8
  94 bg_BG
  95 bg_BG.utf8
  96 br_FR
  97 bs_BA
  98 C
  99 ca_ES
 100 ca_ES@euro
 101 ca_ES.utf8
 102 ca_ES.utf8@euro
 103 cs_CZ
 104 cs_CZ.utf8
 105 cy_GB
 106 da_DK
 107 da_DK.iso885915
 108 da_DK.utf8
 109 de_AT
 110 de_AT@euro
 111 de_AT.utf8
 112 de_AT.utf8@euro
 113 de_BE
 114 de_BE@euro
 115 de_BE.utf8
 116 de_BE.utf8@euro
 117 de_CH
 118 de_CH.utf8
 119 de_DE
 120 de_DE@euro
 121 de_DE.utf8
 122 de_DE.utf8@euro
 123 de_LU
 124 de_LU@euro
 125 de_LU.utf8
 126 de_LU.utf8@euro
 127 el_GR
 128 el_GR.utf8
 129 en_AU
 130 en_AU.utf8
 131 en_BW
 132 en_BW.utf8
 133 en_CA
 134 en_CA.utf8
 135 en_DK
 136 en_DK.utf8
 137 en_GB
 138 en_GB.iso885915
 139 en_GB.utf8
 140 en_HK
 141 en_HK.utf8
 142 en_IE
 143 en_IE@euro
 144 en_IE.utf8
 145 en_IE.utf8@euro
 146 en_IN
 147 en_NZ
 148 en_NZ.utf8
 149 en_PH
 150 en_PH.utf8
 151 en_SG
 152 en_SG.utf8
 153 en_US
 154 en_US.iso885915
 155 en_US.utf8
 156 en_ZA
 157 en_ZA.utf8
 158 en_ZW
 159 en_ZW.utf8
 160 es_AR
 161 es_AR.utf8
 162 es_BO
 163 es_BO.utf8
 164 es_CL
 165 es_CL.utf8
 166 es_CO
 167 es_CO.utf8
 168 es_CR
 169 es_CR.utf8
 170 es_DO
 171 es_DO.utf8
 172 es_EC
 173 es_EC.utf8
 174 es_ES
 175 es_ES@euro
 176 es_ES.utf8
 177 es_ES.utf8@euro
 178 es_GT
 179 es_GT.utf8
 180 es_HN
 181 es_HN.utf8
 182 es_MX
 183 es_MX.utf8
 184 es_NI
 185 es_NI.utf8
 186 es_PA
 187 es_PA.utf8
 188 es_PE
 189 es_PE.utf8
 190 es_PR
 191 es_PR.utf8
 192 es_PY
 193 es_PY.utf8
 194 es_SV
 195 es_SV.utf8
 196 es_US
 197 es_US.utf8
 198 es_UY
 199 es_UY.utf8
 200 es_VE
 201 es_VE.utf8
 202 et_EE
 203 et_EE.utf8
 204 eu_ES
 205 eu_ES@euro
 206 eu_ES.utf8
 207 eu_ES.utf8@euro
 208 fa_IR
 209 fi_FI
 210 fi_FI@euro
 211 fi_FI.utf8
 212 fi_FI.utf8@euro
 213 fo_FO
 214 fo_FO.utf8
 215 fr_BE
 216 fr_BE@euro
 217 fr_BE.utf8
 218 fr_BE.utf8@euro
 219 fr_CA
 220 fr_CA.utf8
 221 fr_CH
 222 fr_CH.utf8
 223 fr_FR
 224 fr_FR@euro
 225 fr_FR.utf8
 226 fr_FR.utf8@euro
 227 fr_LU
 228 fr_LU@euro
 229 fr_LU.utf8
 230 fr_LU.utf8@euro
 231 ga_IE
 232 ga_IE@euro
 233 ga_IE.utf8
 234 ga_IE.utf8@euro
 235 gl_ES
 236 gl_ES@euro
 237 gl_ES.utf8
 238 gl_ES.utf8@euro
 239 gv_GB
 240 gv_GB.utf8
 241 he_IL
 242 he_IL.utf8
 243 hi_IN
 244 hr_HR
 245 hr_HR.utf8
 246 hu_HU
 247 hu_HU.utf8
 248 id_ID
 249 id_ID.utf8
 250 is_IS
 251 is_IS.utf8
 252 it_CH
 253 it_CH.utf8
 254 it_IT
 255 it_IT@euro
 256 it_IT.utf8
 257 it_IT.utf8@euro
 258 iw_IL
 259 iw_IL.utf8
 260 ja_JP.eucjp
 261 ja_JP.utf8
 262 ka_GE
 263 kl_GL
 264 kl_GL.utf8
 265 ko_KR.euckr
 266 ko_KR.utf8
 267 kw_GB
 268 kw_GB.utf8
 269 lt_LT
 270 lt_LT.utf8
 271 lv_LV
 272 lv_LV.utf8
 273 mi_NZ
 274 mk_MK
 275 mk_MK.utf8
 276 mr_IN
 277 ms_MY
 278 ms_MY.utf8
 279 mt_MT
 280 mt_MT.utf8
 281 nl_BE
 282 nl_BE@euro
 283 nl_BE.utf8
 284 nl_BE.utf8@euro
 285 nl_NL
 286 nl_NL@euro
 287 nl_NL.utf8
 288 nl_NL.utf8@euro
 289 nn_NO
 290 nn_NO.utf8
 291 no_NO
 292 no_NO.utf8
 293 oc_FR
 294 pl_PL
 295 pl_PL.utf8
 296 POSIX
 297 pt_BR
 298 pt_BR.utf8
 299 pt_PT
 300 pt_PT@euro
 301 pt_PT.utf8
 302 pt_PT.utf8@euro
 303 ro_RO
 304 ro_RO.utf8
 305 ru_RU
 306 ru_RU.koi8r
 307 ru_RU.utf8
 308 ru_UA
 309 ru_UA.utf8
 310 se_NO
 311 sk_SK
 312 sk_SK.utf8
 313 sl_SI
 314 sl_SI.utf8
 315 sq_AL
 316 sq_AL.utf8
 317 sr_YU
 318 sr_YU@cyrillic
 319 sr_YU.utf8
 320 sr_YU.utf8@cyrillic
 321 sv_FI
 322 sv_FI@euro
 323 sv_FI.utf8
 324 sv_FI.utf8@euro
 325 sv_SE
 326 sv_SE.iso885915
 327 sv_SE.utf8
 328 ta_IN
 329 te_IN
 330 tg_TJ
 331 th_TH
 332 th_TH.utf8
 333 tl_PH
 334 tr_TR
 335 tr_TR.utf8
 336 uk_UA
 337 uk_UA.utf8
 338 ur_PK
 339 uz_UZ
 340 vi_VN
 341 vi_VN.tcvn
 342 wa_BE
 343 wa_BE@euro
 344 yi_US
 345 zh_CN
 346 zh_CN.gb18030
 347 zh_CN.gbk
 348 zh_CN.utf8
 349 zh_HK
 350 zh_HK.utf8
 351 zh_TW
 352 zh_TW.euctw
 353 zh_TW.utf8
 354 </pre></blockquote></div></li><li class="listitem"><p>
 355        <code class="code">`locale`</code> displays environmental variables that
 356        impact how locale("") will be deduced.
 357      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
 358 LANG=en_US
 359 LC_CTYPE="en_US"
 360 LC_NUMERIC="en_US"
 361 LC_TIME="en_US"
 362 LC_COLLATE="en_US"
 363 LC_MONETARY="en_US"
 364 LC_MESSAGES="en_US"
 365 LC_PAPER="en_US"
 366 LC_NAME="en_US"
 367 LC_ADDRESS="en_US"
 368 LC_TELEPHONE="en_US"
 369 LC_MEASUREMENT="en_US"
 370 LC_IDENTIFICATION="en_US"
 371 LC_ALL=
 372 </pre></blockquote></div></li></ul></div><p>
 373 From Josuttis, p. 697-698, which says, that "there is only *one*
 374 relation (of the C++ locale mechanism) to the C locale mechanism: the
 375 global C locale is modified if a named C++ locale object is set as the
 376 global locale" (emphasis Paolo), that is:
 377 </p><pre class="programlisting">std::locale::global(std::locale(""));</pre><p>affects the C functions as if the following call was made:</p><pre class="programlisting">std::setlocale(LC_ALL, "");</pre><p>
 378   On the other hand, there is *no* vice versa, that is, calling
 379   setlocale has *no* whatsoever on the C++ locale mechanism, in
 380   particular on the working of locale(""), which constructs the locale
 381   object from the environment of the running program, that is, in
 382   practice, the set of LC_ALL, LANG, etc. variable of the shell.
 383 </p></div></div><div class="sect2" title="Future"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.future"></a>Future</h3></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
 384        Locale initialization: at what point does _S_classic, _S_global
 385        get initialized? Can named locales assume this initialization
 386        has already taken place?
 387      </p></li><li class="listitem"><p>
 388        Document how named locales error check when filling data
 389        members. I.e., a fr_FR locale that doesn't have
 390        numpunct::truename(): does it use "true"? Or is it a blank
 391        string? What's the convention?
 392    </p></li><li class="listitem"><p>
 393        Explain how locale aliasing happens. When does "de_DE" use "de"
 394        information? What is the rule for locales composed of just an
 395        ISO language code (say, "de") and locales with both an ISO
 396        language code and ISO country code (say, "de_DE").
 397      </p></li><li class="listitem"><p>
 398        What should non-required facet instantiations do?  If the
 399        generic implementation is provided, then how to end-users
 400        provide specializations?
 401    </p></li></ul></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry" title="The GNU C Library"><a id="id508650"></a><p><span class="title"><i>
 402       The GNU C Library
 403     </i>. </span><span class="author"><span class="firstname">Roland</span> <span class="surname">McGrath</span>. </span><span class="author"><span class="firstname">Ulrich</span> <span class="surname">Drepper</span>. </span><span class="copyright">Copyright © 2007 FSF. </span><span class="pagenums">Chapters 6 Character Set Handling and 7 Locales and Internationalization. </span></p></div><div class="biblioentry" title="Correspondence"><a id="id448472"></a><p><span class="title"><i>
 404       Correspondence
 405     </i>. </span><span class="author"><span class="firstname">Ulrich</span> <span class="surname">Drepper</span>. </span><span class="copyright">Copyright © 2002 . </span></p></div><div class="biblioentry" title="ISO/IEC 14882:1998 Programming languages - C++"><a id="id429400"></a><p><span class="title"><i>
 406       ISO/IEC 14882:1998 Programming languages - C++
 407     </i>. </span><span class="copyright">Copyright © 1998 ISO. </span></p></div><div class="biblioentry" title="ISO/IEC 9899:1999 Programming languages - C"><a id="id429418"></a><p><span class="title"><i>
 408       ISO/IEC 9899:1999 Programming languages - C
 409     </i>. </span><span class="copyright">Copyright © 1999 ISO. </span></p></div><div class="biblioentry" title="The Open Group Base Specifications, Issue 6 (IEEE Std. 1003.1-2004)"><a id="id474897"></a><p><span class="title"><i>
 410       The Open Group Base Specifications, Issue 6 (IEEE Std. 1003.1-2004)
 411     </i>. </span><span class="copyright">Copyright © 1999
 412       The Open Group/The Institute of Electrical and Electronics Engineers, Inc.. </span><span class="biblioid">
 413       <a class="ulink" href="http://www.unix.org/version3/ieee_std.html" target="_top">
 414       </a>
 415     . </span></p></div><div class="biblioentry" title="The C++ Programming Language, Special Edition"><a id="id474924"></a><p><span class="title"><i>
 416       The C++ Programming Language, Special Edition
 417     </i>. </span><span class="author"><span class="firstname">Bjarne</span> <span class="surname">Stroustrup</span>. </span><span class="copyright">Copyright © 2000 Addison Wesley, Inc.. </span><span class="pagenums">Appendix D. </span><span class="publisher"><span class="publishername">
 418         Addison Wesley
 419       . </span></span></p></div><div class="biblioentry" title="Standard C++ IOStreams and Locales"><a id="id436766"></a><p><span class="title"><i>
 420       Standard C++ IOStreams and Locales
 421     </i>. </span><span class="subtitle">
 422       Advanced Programmer's Guide and Reference
 423     . </span><span class="author"><span class="firstname">Angelika</span> <span class="surname">Langer</span>. </span><span class="author"><span class="firstname">Klaus</span> <span class="surname">Kreft</span>. </span><span class="copyright">Copyright © 2000 Addison Wesley Longman, Inc.. </span><span class="publisher"><span class="publishername">
 424         Addison Wesley Longman
 425       . </span></span></p></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="localization.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="localization.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="facets.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part VI.
 426   Localization
 427
 428  </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 15. Facets aka Categories</td></tr></table></div></body></html>