libstdc++-v3/doc/html/manual/localization.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 8.  Localization</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="bk01pt02.html" title="Part II.  Standard Contents" /><link rel="prev" href="strings.html" title="Chapter 7.  Strings" /><link rel="next" href="facets.html" title="Facets" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 8.
   4   Localization
   5
   6 </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="strings.html">Prev</a> </td><th width="60%" align="center">Part II.
   7   Standard Contents
   8 </th><td width="20%" align="right"> <a accesskey="n" href="facets.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 8.  Localization"><div class="titlepage"><div><div><h2 class="title"><a id="std.localization"></a>Chapter 8.
   9   Localization
  10   <a id="id601252" class="indexterm"></a>
  11 </h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="localization.html#std.localization.locales">Locales</a></span></dt><dd><dl><dt><span class="section"><a href="localization.html#std.localization.locales.locale">locale</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html">Facets</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#std.localization.facet.ctype">ctype</a></span></dt><dt><span class="section"><a href="facets.html#std.localization.facet.codecvt">codecvt</a></span></dt><dt><span class="section"><a href="facets.html#manual.localization.facet.messages">messages</a></span></dt></dl></dd></dl></div><div class="section" title="Locales"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.localization.locales"></a>Locales</h2></div></div></div><div class="section" title="locale"><div class="titlepage"><div><div><h3 class="title"><a id="std.localization.locales.locale"></a>locale</h3></div></div></div><p>
  12 Describes the basic locale object, including nested
  13 classes id, facet, and the reference-counted implementation object,
  14 class _Impl.
  15 </p><div class="section" title="Requirements"><div class="titlepage"><div><div><h4 class="title"><a id="locales.locale.req"></a>Requirements</h4></div></div></div><p>
  16 Class locale is non-templatized and has two distinct types nested
  17 inside of it:
  18 </p><div class="blockquote"><blockquote class="blockquote"><p>
  19 <span class="emphasis"><em>
  20 class facet
  21 22.1.1.1.2 Class locale::facet
  22 </em></span>
  23 </p></blockquote></div><p>
  24 Facets actually implement locale functionality. For instance, a facet
  25 called numpunct is the data object that can be used to query for the
  26 thousands separator in the locale.
  27 </p><p>
  28 Literally, a facet is strictly defined:
  29 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  30       Containing the following public data member:
  31     </p><p>
  32       <code class="code">static locale::id id;</code>
  33     </p></li><li class="listitem"><p>
  34       Derived from another facet:
  35     </p><p>
  36       <code class="code">class gnu_codecvt: public std::ctype&lt;user-defined-type&gt;</code>
  37     </p></li></ul></div><p>
  38 Of interest in this class are the memory management options explicitly
  39 specified as an argument to facet's constructor. Each constructor of a
  40 facet class takes a std::size_t __refs argument: if __refs == 0, the
  41 facet is deleted when the locale containing it is destroyed. If __refs
  42 == 1, the facet is not destroyed, even when it is no longer
  43 referenced.
  44 </p><div class="blockquote"><blockquote class="blockquote"><p>
  45 <span class="emphasis"><em>
  46 class id
  47 22.1.1.1.3 - Class locale::id
  48 </em></span>
  49 </p></blockquote></div><p>
  50 Provides an index for looking up specific facets.
  51 </p></div><div class="section" title="Design"><div class="titlepage"><div><div><h4 class="title"><a id="locales.locale.design"></a>Design</h4></div></div></div><p>
  52 The major design challenge is fitting an object-orientated and
  53 non-global locale design on top of POSIX and other relevant standards,
  54 which include the Single Unix (nee X/Open.)
  55 </p><p>
  56 Because C and earlier versions of POSIX fall down so completely,
  57 portability is an issue.
  58 </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a id="locales.locale.impl"></a>Implementation</h4></div></div></div><div class="section" title="Interacting with &quot;C&quot; locales"><div class="titlepage"><div><div><h5 class="title"><a id="locale.impl.c"></a>Interacting with "C" locales</h5></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  59        <code class="code">`locale -a`</code> displays available locales.
  60      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
  61 af_ZA
  62 ar_AE
  63 ar_AE.utf8
  64 ar_BH
  65 ar_BH.utf8
  66 ar_DZ
  67 ar_DZ.utf8
  68 ar_EG
  69 ar_EG.utf8
  70 ar_IN
  71 ar_IQ
  72 ar_IQ.utf8
  73 ar_JO
  74 ar_JO.utf8
  75 ar_KW
  76 ar_KW.utf8
  77 ar_LB
  78 ar_LB.utf8
  79 ar_LY
  80 ar_LY.utf8
  81 ar_MA
  82 ar_MA.utf8
  83 ar_OM
  84 ar_OM.utf8
  85 ar_QA
  86 ar_QA.utf8
  87 ar_SA
  88 ar_SA.utf8
  89 ar_SD
  90 ar_SD.utf8
  91 ar_SY
  92 ar_SY.utf8
  93 ar_TN
  94 ar_TN.utf8
  95 ar_YE
  96 ar_YE.utf8
  97 be_BY
  98 be_BY.utf8
  99 bg_BG
 100 bg_BG.utf8
 101 br_FR
 102 bs_BA
 103 C
 104 ca_ES
 105 ca_ES@euro
 106 ca_ES.utf8
 107 ca_ES.utf8@euro
 108 cs_CZ
 109 cs_CZ.utf8
 110 cy_GB
 111 da_DK
 112 da_DK.iso885915
 113 da_DK.utf8
 114 de_AT
 115 de_AT@euro
 116 de_AT.utf8
 117 de_AT.utf8@euro
 118 de_BE
 119 de_BE@euro
 120 de_BE.utf8
 121 de_BE.utf8@euro
 122 de_CH
 123 de_CH.utf8
 124 de_DE
 125 de_DE@euro
 126 de_DE.utf8
 127 de_DE.utf8@euro
 128 de_LU
 129 de_LU@euro
 130 de_LU.utf8
 131 de_LU.utf8@euro
 132 el_GR
 133 el_GR.utf8
 134 en_AU
 135 en_AU.utf8
 136 en_BW
 137 en_BW.utf8
 138 en_CA
 139 en_CA.utf8
 140 en_DK
 141 en_DK.utf8
 142 en_GB
 143 en_GB.iso885915
 144 en_GB.utf8
 145 en_HK
 146 en_HK.utf8
 147 en_IE
 148 en_IE@euro
 149 en_IE.utf8
 150 en_IE.utf8@euro
 151 en_IN
 152 en_NZ
 153 en_NZ.utf8
 154 en_PH
 155 en_PH.utf8
 156 en_SG
 157 en_SG.utf8
 158 en_US
 159 en_US.iso885915
 160 en_US.utf8
 161 en_ZA
 162 en_ZA.utf8
 163 en_ZW
 164 en_ZW.utf8
 165 es_AR
 166 es_AR.utf8
 167 es_BO
 168 es_BO.utf8
 169 es_CL
 170 es_CL.utf8
 171 es_CO
 172 es_CO.utf8
 173 es_CR
 174 es_CR.utf8
 175 es_DO
 176 es_DO.utf8
 177 es_EC
 178 es_EC.utf8
 179 es_ES
 180 es_ES@euro
 181 es_ES.utf8
 182 es_ES.utf8@euro
 183 es_GT
 184 es_GT.utf8
 185 es_HN
 186 es_HN.utf8
 187 es_MX
 188 es_MX.utf8
 189 es_NI
 190 es_NI.utf8
 191 es_PA
 192 es_PA.utf8
 193 es_PE
 194 es_PE.utf8
 195 es_PR
 196 es_PR.utf8
 197 es_PY
 198 es_PY.utf8
 199 es_SV
 200 es_SV.utf8
 201 es_US
 202 es_US.utf8
 203 es_UY
 204 es_UY.utf8
 205 es_VE
 206 es_VE.utf8
 207 et_EE
 208 et_EE.utf8
 209 eu_ES
 210 eu_ES@euro
 211 eu_ES.utf8
 212 eu_ES.utf8@euro
 213 fa_IR
 214 fi_FI
 215 fi_FI@euro
 216 fi_FI.utf8
 217 fi_FI.utf8@euro
 218 fo_FO
 219 fo_FO.utf8
 220 fr_BE
 221 fr_BE@euro
 222 fr_BE.utf8
 223 fr_BE.utf8@euro
 224 fr_CA
 225 fr_CA.utf8
 226 fr_CH
 227 fr_CH.utf8
 228 fr_FR
 229 fr_FR@euro
 230 fr_FR.utf8
 231 fr_FR.utf8@euro
 232 fr_LU
 233 fr_LU@euro
 234 fr_LU.utf8
 235 fr_LU.utf8@euro
 236 ga_IE
 237 ga_IE@euro
 238 ga_IE.utf8
 239 ga_IE.utf8@euro
 240 gl_ES
 241 gl_ES@euro
 242 gl_ES.utf8
 243 gl_ES.utf8@euro
 244 gv_GB
 245 gv_GB.utf8
 246 he_IL
 247 he_IL.utf8
 248 hi_IN
 249 hr_HR
 250 hr_HR.utf8
 251 hu_HU
 252 hu_HU.utf8
 253 id_ID
 254 id_ID.utf8
 255 is_IS
 256 is_IS.utf8
 257 it_CH
 258 it_CH.utf8
 259 it_IT
 260 it_IT@euro
 261 it_IT.utf8
 262 it_IT.utf8@euro
 263 iw_IL
 264 iw_IL.utf8
 265 ja_JP.eucjp
 266 ja_JP.utf8
 267 ka_GE
 268 kl_GL
 269 kl_GL.utf8
 270 ko_KR.euckr
 271 ko_KR.utf8
 272 kw_GB
 273 kw_GB.utf8
 274 lt_LT
 275 lt_LT.utf8
 276 lv_LV
 277 lv_LV.utf8
 278 mi_NZ
 279 mk_MK
 280 mk_MK.utf8
 281 mr_IN
 282 ms_MY
 283 ms_MY.utf8
 284 mt_MT
 285 mt_MT.utf8
 286 nl_BE
 287 nl_BE@euro
 288 nl_BE.utf8
 289 nl_BE.utf8@euro
 290 nl_NL
 291 nl_NL@euro
 292 nl_NL.utf8
 293 nl_NL.utf8@euro
 294 nn_NO
 295 nn_NO.utf8
 296 no_NO
 297 no_NO.utf8
 298 oc_FR
 299 pl_PL
 300 pl_PL.utf8
 301 POSIX
 302 pt_BR
 303 pt_BR.utf8
 304 pt_PT
 305 pt_PT@euro
 306 pt_PT.utf8
 307 pt_PT.utf8@euro
 308 ro_RO
 309 ro_RO.utf8
 310 ru_RU
 311 ru_RU.koi8r
 312 ru_RU.utf8
 313 ru_UA
 314 ru_UA.utf8
 315 se_NO
 316 sk_SK
 317 sk_SK.utf8
 318 sl_SI
 319 sl_SI.utf8
 320 sq_AL
 321 sq_AL.utf8
 322 sr_YU
 323 sr_YU@cyrillic
 324 sr_YU.utf8
 325 sr_YU.utf8@cyrillic
 326 sv_FI
 327 sv_FI@euro
 328 sv_FI.utf8
 329 sv_FI.utf8@euro
 330 sv_SE
 331 sv_SE.iso885915
 332 sv_SE.utf8
 333 ta_IN
 334 te_IN
 335 tg_TJ
 336 th_TH
 337 th_TH.utf8
 338 tl_PH
 339 tr_TR
 340 tr_TR.utf8
 341 uk_UA
 342 uk_UA.utf8
 343 ur_PK
 344 uz_UZ
 345 vi_VN
 346 vi_VN.tcvn
 347 wa_BE
 348 wa_BE@euro
 349 yi_US
 350 zh_CN
 351 zh_CN.gb18030
 352 zh_CN.gbk
 353 zh_CN.utf8
 354 zh_HK
 355 zh_HK.utf8
 356 zh_TW
 357 zh_TW.euctw
 358 zh_TW.utf8
 359 </pre></blockquote></div></li><li class="listitem"><p>
 360        <code class="code">`locale`</code> displays environmental variables that
 361        impact how locale("") will be deduced.
 362      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
 363 LANG=en_US
 364 LC_CTYPE="en_US"
 365 LC_NUMERIC="en_US"
 366 LC_TIME="en_US"
 367 LC_COLLATE="en_US"
 368 LC_MONETARY="en_US"
 369 LC_MESSAGES="en_US"
 370 LC_PAPER="en_US"
 371 LC_NAME="en_US"
 372 LC_ADDRESS="en_US"
 373 LC_TELEPHONE="en_US"
 374 LC_MEASUREMENT="en_US"
 375 LC_IDENTIFICATION="en_US"
 376 LC_ALL=
 377 </pre></blockquote></div></li></ul></div><p>
 378 From Josuttis, p. 697-698, which says, that "there is only *one*
 379 relation (of the C++ locale mechanism) to the C locale mechanism: the
 380 global C locale is modified if a named C++ locale object is set as the
 381 global locale" (emphasis Paolo), that is:
 382 </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>
 383   On the other hand, there is *no* vice versa, that is, calling
 384   setlocale has *no* whatsoever on the C++ locale mechanism, in
 385   particular on the working of locale(""), which constructs the locale
 386   object from the environment of the running program, that is, in
 387   practice, the set of LC_ALL, LANG, etc. variable of the shell.
 388 </p></div></div><div class="section" title="Future"><div class="titlepage"><div><div><h4 class="title"><a id="locales.locale.future"></a>Future</h4></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
 389        Locale initialization: at what point does _S_classic, _S_global
 390        get initialized? Can named locales assume this initialization
 391        has already taken place?
 392      </p></li><li class="listitem"><p>
 393        Document how named locales error check when filling data
 394        members. I.e., a fr_FR locale that doesn't have
 395        numpunct::truename(): does it use "true"? Or is it a blank
 396        string? What's the convention?
 397    </p></li><li class="listitem"><p>
 398        Explain how locale aliasing happens. When does "de_DE" use "de"
 399        information? What is the rule for locales composed of just an
 400        ISO language code (say, "de") and locales with both an ISO
 401        language code and ISO country code (say, "de_DE").
 402      </p></li><li class="listitem"><p>
 403        What should non-required facet instantiations do?  If the
 404        generic implementation is provided, then how to end-users
 405        provide specializations?
 406    </p></li></ul></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h4 class="title"><a id="locales.locale.biblio"></a>Bibliography</h4></div></div></div><div class="biblioentry" title="The GNU C Library"><a id="id541662"></a><p><span class="title"><i>
 407       The GNU C Library
 408     </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">
 409       Chapters 6 Character Set Handling and 7 Locales and
 410       Internationalization
 411     . </span></p></div><div class="biblioentry" title="Correspondence"><a id="id567498"></a><p><span class="title"><i>
 412       Correspondence
 413     </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="id628132"></a><p><span class="title"><i>
 414       ISO/IEC 14882:1998 Programming languages - C++
 415     </i>. </span><span class="copyright">Copyright © 1998 ISO. </span></p></div><div class="biblioentry" title="ISO/IEC 9899:1999 Programming languages - C"><a id="id602622"></a><p><span class="title"><i>
 416       ISO/IEC 9899:1999 Programming languages - C
 417     </i>. </span><span class="copyright">Copyright © 1999 ISO. </span></p></div><div class="biblioentry"><a id="id602640"></a><p><span class="biblioid">
 418       <a class="ulink" href="http://www.opengroup.org/austin" target="_top">
 419         <em class="citetitle">
 420           System Interface Definitions, Issue 7 (IEEE Std. 1003.1-2008)
 421         </em>
 422       </a>
 423     . </span><span class="copyright">Copyright © 2008
 424         The Open Group/The Institute of Electrical and Electronics
 425         Engineers, Inc.
 426       . </span></p></div><div class="biblioentry" title="The C++ Programming Language, Special Edition"><a id="id551395"></a><p><span class="title"><i>
 427       The C++ Programming Language, Special Edition
 428     </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">
 429         Addison Wesley
 430       . </span></span></p></div><div class="biblioentry" title="Standard C++ IOStreams and Locales"><a id="id560241"></a><p><span class="title"><i>
 431       Standard C++ IOStreams and Locales
 432     </i>. </span><span class="subtitle">
 433       Advanced Programmer's Guide and Reference
 434     . </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">
 435         Addison Wesley Longman
 436       . </span></span></p></div></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="strings.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt02.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">Chapter 7.
 437   Strings
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