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  11     "><link rel="home" href="../index.html" title="The GNU C++ Library"><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 bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 8.
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  17   Localization
  18   <a class="indexterm" name="id624511"></a>
  19 </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><dd><dl><dt><span class="section"><a href="localization.html#locales.locale.req">Requirements</a></span></dt><dt><span class="section"><a href="localization.html#locales.locale.design">Design</a></span></dt><dt><span class="section"><a href="localization.html#locales.locale.impl">Implementation</a></span></dt><dd><dl><dt><span class="section"><a href="localization.html#locale.impl.c">Interacting with "C" locales</a></span></dt></dl></dd><dt><span class="section"><a href="localization.html#locales.locale.future">Future</a></span></dt></dl></dd></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><dd><dl><dt><span class="section"><a href="facets.html#facet.ctype.impl">Implementation</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#id625164">Specializations</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html#facet.ctype.future">Future</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html#std.localization.facet.codecvt">codecvt</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#facet.codecvt.req">Requirements</a></span></dt><dt><span class="section"><a href="facets.html#facet.codecvt.design">Design</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#codecvt.design.wchar_t_size"><span class="type">wchar_t</span> Size</a></span></dt><dt><span class="section"><a href="facets.html#codecvt.design.unicode">Support for Unicode</a></span></dt><dt><span class="section"><a href="facets.html#codecvt.design.issues">Other Issues</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html#facet.codecvt.impl">Implementation</a></span></dt><dt><span class="section"><a href="facets.html#facet.codecvt.use">Use</a></span></dt><dt><span class="section"><a href="facets.html#facet.codecvt.future">Future</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html#manual.localization.facet.messages">messages</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#facet.messages.req">Requirements</a></span></dt><dt><span class="section"><a href="facets.html#facet.messages.design">Design</a></span></dt><dt><span class="section"><a href="facets.html#facet.messages.impl">Implementation</a></span></dt><dd><dl><dt><span class="section"><a href="facets.html#messages.impl.models">Models</a></span></dt><dt><span class="section"><a href="facets.html#messages.impl.gnu">The GNU Model</a></span></dt></dl></dd><dt><span class="section"><a href="facets.html#facet.messages.use">Use</a></span></dt><dt><span class="section"><a href="facets.html#facet.messages.future">Future</a></span></dt></dl></dd></dl></dd></dl></div><div class="section" title="Locales"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="std.localization.locales"></a>Locales</h2></div></div></div><div class="section" title="locale"><div class="titlepage"><div><div><h3 class="title"><a name="std.localization.locales.locale"></a>locale</h3></div></div></div><p>
  20 Describes the basic locale object, including nested
  21 classes id, facet, and the reference-counted implementation object,
  22 class _Impl.
  23 </p><div class="section" title="Requirements"><div class="titlepage"><div><div><h4 class="title"><a name="locales.locale.req"></a>Requirements</h4></div></div></div><p>
  24 Class locale is non-templatized and has two distinct types nested
  25 inside of it:
  26 </p><div class="blockquote"><blockquote class="blockquote"><p>
  27 <span class="emphasis"><em>
  28 class facet
  29 22.1.1.1.2 Class locale::facet
  30 </em></span>
  31 </p></blockquote></div><p>
  32 Facets actually implement locale functionality. For instance, a facet
  33 called numpunct is the data object that can be used to query for the
  34 thousands separator in the locale.
  35 </p><p>
  36 Literally, a facet is strictly defined:
  37 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  38       Containing the following public data member:
  39     </p><p>
  40       <code class="code">static locale::id id;</code>
  41     </p></li><li class="listitem"><p>
  42       Derived from another facet:
  43     </p><p>
  44       <code class="code">class gnu_codecvt: public std::ctype&lt;user-defined-type&gt;</code>
  45     </p></li></ul></div><p>
  46 Of interest in this class are the memory management options explicitly
  47 specified as an argument to facet's constructor. Each constructor of a
  48 facet class takes a std::size_t __refs argument: if __refs == 0, the
  49 facet is deleted when the locale containing it is destroyed. If __refs
  50 == 1, the facet is not destroyed, even when it is no longer
  51 referenced.
  52 </p><div class="blockquote"><blockquote class="blockquote"><p>
  53 <span class="emphasis"><em>
  54 class id
  55 22.1.1.1.3 - Class locale::id
  56 </em></span>
  57 </p></blockquote></div><p>
  58 Provides an index for looking up specific facets.
  59 </p></div><div class="section" title="Design"><div class="titlepage"><div><div><h4 class="title"><a name="locales.locale.design"></a>Design</h4></div></div></div><p>
  60 The major design challenge is fitting an object-orientated and
  61 non-global locale design on top of POSIX and other relevant standards,
  62 which include the Single Unix (nee X/Open.)
  63 </p><p>
  64 Because C and earlier versions of POSIX fall down so completely,
  65 portability is an issue.
  66 </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a name="locales.locale.impl"></a>Implementation</h4></div></div></div><div class="section" title='Interacting with "C" locales'><div class="titlepage"><div><div><h5 class="title"><a name="locale.impl.c"></a>Interacting with "C" locales</h5></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  67        <code class="code">`locale -a`</code> displays available locales.
  68      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
  69 af_ZA
  70 ar_AE
  71 ar_AE.utf8
  72 ar_BH
  73 ar_BH.utf8
  74 ar_DZ
  75 ar_DZ.utf8
  76 ar_EG
  77 ar_EG.utf8
  78 ar_IN
  79 ar_IQ
  80 ar_IQ.utf8
  81 ar_JO
  82 ar_JO.utf8
  83 ar_KW
  84 ar_KW.utf8
  85 ar_LB
  86 ar_LB.utf8
  87 ar_LY
  88 ar_LY.utf8
  89 ar_MA
  90 ar_MA.utf8
  91 ar_OM
  92 ar_OM.utf8
  93 ar_QA
  94 ar_QA.utf8
  95 ar_SA
  96 ar_SA.utf8
  97 ar_SD
  98 ar_SD.utf8
  99 ar_SY
 100 ar_SY.utf8
 101 ar_TN
 102 ar_TN.utf8
 103 ar_YE
 104 ar_YE.utf8
 105 be_BY
 106 be_BY.utf8
 107 bg_BG
 108 bg_BG.utf8
 109 br_FR
 110 bs_BA
 111 C
 112 ca_ES
 113 ca_ES@euro
 114 ca_ES.utf8
 115 ca_ES.utf8@euro
 116 cs_CZ
 117 cs_CZ.utf8
 118 cy_GB
 119 da_DK
 120 da_DK.iso885915
 121 da_DK.utf8
 122 de_AT
 123 de_AT@euro
 124 de_AT.utf8
 125 de_AT.utf8@euro
 126 de_BE
 127 de_BE@euro
 128 de_BE.utf8
 129 de_BE.utf8@euro
 130 de_CH
 131 de_CH.utf8
 132 de_DE
 133 de_DE@euro
 134 de_DE.utf8
 135 de_DE.utf8@euro
 136 de_LU
 137 de_LU@euro
 138 de_LU.utf8
 139 de_LU.utf8@euro
 140 el_GR
 141 el_GR.utf8
 142 en_AU
 143 en_AU.utf8
 144 en_BW
 145 en_BW.utf8
 146 en_CA
 147 en_CA.utf8
 148 en_DK
 149 en_DK.utf8
 150 en_GB
 151 en_GB.iso885915
 152 en_GB.utf8
 153 en_HK
 154 en_HK.utf8
 155 en_IE
 156 en_IE@euro
 157 en_IE.utf8
 158 en_IE.utf8@euro
 159 en_IN
 160 en_NZ
 161 en_NZ.utf8
 162 en_PH
 163 en_PH.utf8
 164 en_SG
 165 en_SG.utf8
 166 en_US
 167 en_US.iso885915
 168 en_US.utf8
 169 en_ZA
 170 en_ZA.utf8
 171 en_ZW
 172 en_ZW.utf8
 173 es_AR
 174 es_AR.utf8
 175 es_BO
 176 es_BO.utf8
 177 es_CL
 178 es_CL.utf8
 179 es_CO
 180 es_CO.utf8
 181 es_CR
 182 es_CR.utf8
 183 es_DO
 184 es_DO.utf8
 185 es_EC
 186 es_EC.utf8
 187 es_ES
 188 es_ES@euro
 189 es_ES.utf8
 190 es_ES.utf8@euro
 191 es_GT
 192 es_GT.utf8
 193 es_HN
 194 es_HN.utf8
 195 es_MX
 196 es_MX.utf8
 197 es_NI
 198 es_NI.utf8
 199 es_PA
 200 es_PA.utf8
 201 es_PE
 202 es_PE.utf8
 203 es_PR
 204 es_PR.utf8
 205 es_PY
 206 es_PY.utf8
 207 es_SV
 208 es_SV.utf8
 209 es_US
 210 es_US.utf8
 211 es_UY
 212 es_UY.utf8
 213 es_VE
 214 es_VE.utf8
 215 et_EE
 216 et_EE.utf8
 217 eu_ES
 218 eu_ES@euro
 219 eu_ES.utf8
 220 eu_ES.utf8@euro
 221 fa_IR
 222 fi_FI
 223 fi_FI@euro
 224 fi_FI.utf8
 225 fi_FI.utf8@euro
 226 fo_FO
 227 fo_FO.utf8
 228 fr_BE
 229 fr_BE@euro
 230 fr_BE.utf8
 231 fr_BE.utf8@euro
 232 fr_CA
 233 fr_CA.utf8
 234 fr_CH
 235 fr_CH.utf8
 236 fr_FR
 237 fr_FR@euro
 238 fr_FR.utf8
 239 fr_FR.utf8@euro
 240 fr_LU
 241 fr_LU@euro
 242 fr_LU.utf8
 243 fr_LU.utf8@euro
 244 ga_IE
 245 ga_IE@euro
 246 ga_IE.utf8
 247 ga_IE.utf8@euro
 248 gl_ES
 249 gl_ES@euro
 250 gl_ES.utf8
 251 gl_ES.utf8@euro
 252 gv_GB
 253 gv_GB.utf8
 254 he_IL
 255 he_IL.utf8
 256 hi_IN
 257 hr_HR
 258 hr_HR.utf8
 259 hu_HU
 260 hu_HU.utf8
 261 id_ID
 262 id_ID.utf8
 263 is_IS
 264 is_IS.utf8
 265 it_CH
 266 it_CH.utf8
 267 it_IT
 268 it_IT@euro
 269 it_IT.utf8
 270 it_IT.utf8@euro
 271 iw_IL
 272 iw_IL.utf8
 273 ja_JP.eucjp
 274 ja_JP.utf8
 275 ka_GE
 276 kl_GL
 277 kl_GL.utf8
 278 ko_KR.euckr
 279 ko_KR.utf8
 280 kw_GB
 281 kw_GB.utf8
 282 lt_LT
 283 lt_LT.utf8
 284 lv_LV
 285 lv_LV.utf8
 286 mi_NZ
 287 mk_MK
 288 mk_MK.utf8
 289 mr_IN
 290 ms_MY
 291 ms_MY.utf8
 292 mt_MT
 293 mt_MT.utf8
 294 nl_BE
 295 nl_BE@euro
 296 nl_BE.utf8
 297 nl_BE.utf8@euro
 298 nl_NL
 299 nl_NL@euro
 300 nl_NL.utf8
 301 nl_NL.utf8@euro
 302 nn_NO
 303 nn_NO.utf8
 304 no_NO
 305 no_NO.utf8
 306 oc_FR
 307 pl_PL
 308 pl_PL.utf8
 309 POSIX
 310 pt_BR
 311 pt_BR.utf8
 312 pt_PT
 313 pt_PT@euro
 314 pt_PT.utf8
 315 pt_PT.utf8@euro
 316 ro_RO
 317 ro_RO.utf8
 318 ru_RU
 319 ru_RU.koi8r
 320 ru_RU.utf8
 321 ru_UA
 322 ru_UA.utf8
 323 se_NO
 324 sk_SK
 325 sk_SK.utf8
 326 sl_SI
 327 sl_SI.utf8
 328 sq_AL
 329 sq_AL.utf8
 330 sr_YU
 331 sr_YU@cyrillic
 332 sr_YU.utf8
 333 sr_YU.utf8@cyrillic
 334 sv_FI
 335 sv_FI@euro
 336 sv_FI.utf8
 337 sv_FI.utf8@euro
 338 sv_SE
 339 sv_SE.iso885915
 340 sv_SE.utf8
 341 ta_IN
 342 te_IN
 343 tg_TJ
 344 th_TH
 345 th_TH.utf8
 346 tl_PH
 347 tr_TR
 348 tr_TR.utf8
 349 uk_UA
 350 uk_UA.utf8
 351 ur_PK
 352 uz_UZ
 353 vi_VN
 354 vi_VN.tcvn
 355 wa_BE
 356 wa_BE@euro
 357 yi_US
 358 zh_CN
 359 zh_CN.gb18030
 360 zh_CN.gbk
 361 zh_CN.utf8
 362 zh_HK
 363 zh_HK.utf8
 364 zh_TW
 365 zh_TW.euctw
 366 zh_TW.utf8
 367 </pre></blockquote></div></li><li class="listitem"><p>
 368        <code class="code">`locale`</code> displays environmental variables that
 369        impact how locale("") will be deduced.
 370      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
 371 LANG=en_US
 372 LC_CTYPE="en_US"
 373 LC_NUMERIC="en_US"
 374 LC_TIME="en_US"
 375 LC_COLLATE="en_US"
 376 LC_MONETARY="en_US"
 377 LC_MESSAGES="en_US"
 378 LC_PAPER="en_US"
 379 LC_NAME="en_US"
 380 LC_ADDRESS="en_US"
 381 LC_TELEPHONE="en_US"
 382 LC_MEASUREMENT="en_US"
 383 LC_IDENTIFICATION="en_US"
 384 LC_ALL=
 385 </pre></blockquote></div></li></ul></div><p>
 386 From Josuttis, p. 697-698, which says, that "there is only *one*
 387 relation (of the C++ locale mechanism) to the C locale mechanism: the
 388 global C locale is modified if a named C++ locale object is set as the
 389 global locale" (emphasis Paolo), that is:
 390 </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>
 391   On the other hand, there is *no* vice versa, that is, calling
 392   setlocale has *no* whatsoever on the C++ locale mechanism, in
 393   particular on the working of locale(""), which constructs the locale
 394   object from the environment of the running program, that is, in
 395   practice, the set of LC_ALL, LANG, etc. variable of the shell.
 396 </p></div></div><div class="section" title="Future"><div class="titlepage"><div><div><h4 class="title"><a name="locales.locale.future"></a>Future</h4></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
 397        Locale initialization: at what point does _S_classic, _S_global
 398        get initialized? Can named locales assume this initialization
 399        has already taken place?
 400      </p></li><li class="listitem"><p>
 401        Document how named locales error check when filling data
 402        members. I.e., a fr_FR locale that doesn't have
 403        numpunct::truename(): does it use "true"? Or is it a blank
 404        string? What's the convention?
 405    </p></li><li class="listitem"><p>
 406        Explain how locale aliasing happens. When does "de_DE" use "de"
 407        information? What is the rule for locales composed of just an
 408        ISO language code (say, "de") and locales with both an ISO
 409        language code and ISO country code (say, "de_DE").
 410      </p></li><li class="listitem"><p>
 411        What should non-required facet instantiations do?  If the
 412        generic implementation is provided, then how to end-users
 413        provide specializations?
 414    </p></li></ul></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h4 class="title"><a name="locales.locale.biblio"></a>Bibliography</h4></div></div></div><div class="biblioentry"><a name="id624874"></a><p><span class="citetitle"><em class="citetitle">
 415       The GNU C Library
 416     </em>. </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">
 417       Chapters 6 Character Set Handling and 7 Locales and
 418       Internationalization
 419     . </span></p></div><div class="biblioentry"><a name="id624914"></a><p><span class="citetitle"><em class="citetitle">
 420       Correspondence
 421     </em>. </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"><a name="id624939"></a><p><span class="citetitle"><em class="citetitle">
 422       ISO/IEC 14882:1998 Programming languages - C++
 423     </em>. </span><span class="copyright">Copyright © 1998 ISO. </span></p></div><div class="biblioentry"><a name="id624958"></a><p><span class="citetitle"><em class="citetitle">
 424       ISO/IEC 9899:1999 Programming languages - C
 425     </em>. </span><span class="copyright">Copyright © 1999 ISO. </span></p></div><div class="biblioentry" title="System Interface Definitions, Issue 7 (IEEE Std. 1003.1-2008)"><a name="id624977"></a><p><span class="title"><i>
 426         <a class="link" href="http://www.opengroup.org/austin/" target="_top">
 427       System Interface Definitions, Issue 7 (IEEE Std. 1003.1-2008)
 428         </a>
 429       </i>. </span><span class="copyright">Copyright © 2008
 430         The Open Group/The Institute of Electrical and Electronics
 431         Engineers, Inc.
 432       . </span></p></div><div class="biblioentry"><a name="id625004"></a><p><span class="citetitle"><em class="citetitle">
 433       The C++ Programming Language, Special Edition
 434     </em>. </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">
 435         Addison Wesley
 436       . </span></span></p></div><div class="biblioentry"><a name="id625043"></a><p><span class="citetitle"><em class="citetitle">
 437       Standard C++ IOStreams and Locales
 438     </em>. </span><span class="subtitle">
 439       Advanced Programmer's Guide and Reference
 440     . </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">
 441         Addison Wesley Longman
 442       . </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.
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