libstdc++-v3/doc/html/manual/bk01pt06ch14.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 V1.73.2" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><link rel="start" 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="bk01pt06ch15.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. Localization</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt06ch15.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><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="bk01pt06ch14.html#manual.localization.locales.locale">locale</a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt06ch14.html#locales.locale.req">Requirements</a></span></dt><dt><span class="sect2"><a href="bk01pt06ch14.html#locales.locale.design">Design</a></span></dt><dt><span class="sect2"><a href="bk01pt06ch14.html#locales.locale.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="bk01pt06ch14.html#locales.locale.future">Future</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.localization.locales.locale"></a>locale</h2></div></div></div><p>
   4 Describes the basic locale object, including nested
   5 classes id, facet, and the reference-counted implementation object,
   6 class _Impl.
   7 </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.req"></a>Requirements</h3></div></div></div><p>
   8 Class locale is non-templatized and has two distinct types nested
   9 inside of it:
  10 </p><div class="blockquote"><blockquote class="blockquote"><p>
  11 <span class="emphasis"><em>
  12 class facet
  13 22.1.1.1.2 Class locale::facet
  14 </em></span>
  15 </p></blockquote></div><p>
  16 Facets actually implement locale functionality. For instance, a facet
  17 called numpunct is the data objects that can be used to query for the
  18 thousands separator is in the German locale.
  19 </p><p>
  20 Literally, a facet is strictly defined:
  21 </p><div class="itemizedlist"><ul type="disc"><li><p>
  22       Containing the following public data member:
  23     </p><p>
  24       <code class="code">static locale::id id;</code>
  25     </p></li><li><p>
  26       Derived from another facet:
  27     </p><p>
  28       <code class="code">class gnu_codecvt: public std::ctype&lt;user-defined-type&gt;</code>
  29     </p></li></ul></div><p>
  30 Of interest in this class are the memory management options explicitly
  31 specified as an argument to facet's constructor. Each constructor of a
  32 facet class takes a std::size_t __refs argument: if __refs == 0, the
  33 facet is deleted when the locale containing it is destroyed. If __refs
  34 == 1, the facet is not destroyed, even when it is no longer
  35 referenced.
  36 </p><div class="blockquote"><blockquote class="blockquote"><p>
  37 <span class="emphasis"><em>
  38 class id
  39 22.1.1.1.3 - Class locale::id
  40 </em></span>
  41 </p></blockquote></div><p>
  42 Provides an index for looking up specific facets.
  43 </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.design"></a>Design</h3></div></div></div><p>
  44 The major design challenge is fitting an object-orientated and
  45 non-global locale design on top of POSIX and other relevant standards,
  46 which include the Single Unix (nee X/Open.)
  47 </p><p>
  48 Because C and earlier versions of POSIX falls down so completely,
  49 portability is an issue.
  50 </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.impl"></a>Implementation</h3></div></div></div><div class="sect3" lang="en" xml:lang="en"><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 type="disc"><li><p>
  51        <code class="code">`locale -a`</code> displays available locales.
  52      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
  53 af_ZA
  54 ar_AE
  55 ar_AE.utf8
  56 ar_BH
  57 ar_BH.utf8
  58 ar_DZ
  59 ar_DZ.utf8
  60 ar_EG
  61 ar_EG.utf8
  62 ar_IN
  63 ar_IQ
  64 ar_IQ.utf8
  65 ar_JO
  66 ar_JO.utf8
  67 ar_KW
  68 ar_KW.utf8
  69 ar_LB
  70 ar_LB.utf8
  71 ar_LY
  72 ar_LY.utf8
  73 ar_MA
  74 ar_MA.utf8
  75 ar_OM
  76 ar_OM.utf8
  77 ar_QA
  78 ar_QA.utf8
  79 ar_SA
  80 ar_SA.utf8
  81 ar_SD
  82 ar_SD.utf8
  83 ar_SY
  84 ar_SY.utf8
  85 ar_TN
  86 ar_TN.utf8
  87 ar_YE
  88 ar_YE.utf8
  89 be_BY
  90 be_BY.utf8
  91 bg_BG
  92 bg_BG.utf8
  93 br_FR
  94 bs_BA
  95 C
  96 ca_ES
  97 ca_ES@euro
  98 ca_ES.utf8
  99 ca_ES.utf8@euro
 100 cs_CZ
 101 cs_CZ.utf8
 102 cy_GB
 103 da_DK
 104 da_DK.iso885915
 105 da_DK.utf8
 106 de_AT
 107 de_AT@euro
 108 de_AT.utf8
 109 de_AT.utf8@euro
 110 de_BE
 111 de_BE@euro
 112 de_BE.utf8
 113 de_BE.utf8@euro
 114 de_CH
 115 de_CH.utf8
 116 de_DE
 117 de_DE@euro
 118 de_DE.utf8
 119 de_DE.utf8@euro
 120 de_LU
 121 de_LU@euro
 122 de_LU.utf8
 123 de_LU.utf8@euro
 124 el_GR
 125 el_GR.utf8
 126 en_AU
 127 en_AU.utf8
 128 en_BW
 129 en_BW.utf8
 130 en_CA
 131 en_CA.utf8
 132 en_DK
 133 en_DK.utf8
 134 en_GB
 135 en_GB.iso885915
 136 en_GB.utf8
 137 en_HK
 138 en_HK.utf8
 139 en_IE
 140 en_IE@euro
 141 en_IE.utf8
 142 en_IE.utf8@euro
 143 en_IN
 144 en_NZ
 145 en_NZ.utf8
 146 en_PH
 147 en_PH.utf8
 148 en_SG
 149 en_SG.utf8
 150 en_US
 151 en_US.iso885915
 152 en_US.utf8
 153 en_ZA
 154 en_ZA.utf8
 155 en_ZW
 156 en_ZW.utf8
 157 es_AR
 158 es_AR.utf8
 159 es_BO
 160 es_BO.utf8
 161 es_CL
 162 es_CL.utf8
 163 es_CO
 164 es_CO.utf8
 165 es_CR
 166 es_CR.utf8
 167 es_DO
 168 es_DO.utf8
 169 es_EC
 170 es_EC.utf8
 171 es_ES
 172 es_ES@euro
 173 es_ES.utf8
 174 es_ES.utf8@euro
 175 es_GT
 176 es_GT.utf8
 177 es_HN
 178 es_HN.utf8
 179 es_MX
 180 es_MX.utf8
 181 es_NI
 182 es_NI.utf8
 183 es_PA
 184 es_PA.utf8
 185 es_PE
 186 es_PE.utf8
 187 es_PR
 188 es_PR.utf8
 189 es_PY
 190 es_PY.utf8
 191 es_SV
 192 es_SV.utf8
 193 es_US
 194 es_US.utf8
 195 es_UY
 196 es_UY.utf8
 197 es_VE
 198 es_VE.utf8
 199 et_EE
 200 et_EE.utf8
 201 eu_ES
 202 eu_ES@euro
 203 eu_ES.utf8
 204 eu_ES.utf8@euro
 205 fa_IR
 206 fi_FI
 207 fi_FI@euro
 208 fi_FI.utf8
 209 fi_FI.utf8@euro
 210 fo_FO
 211 fo_FO.utf8
 212 fr_BE
 213 fr_BE@euro
 214 fr_BE.utf8
 215 fr_BE.utf8@euro
 216 fr_CA
 217 fr_CA.utf8
 218 fr_CH
 219 fr_CH.utf8
 220 fr_FR
 221 fr_FR@euro
 222 fr_FR.utf8
 223 fr_FR.utf8@euro
 224 fr_LU
 225 fr_LU@euro
 226 fr_LU.utf8
 227 fr_LU.utf8@euro
 228 ga_IE
 229 ga_IE@euro
 230 ga_IE.utf8
 231 ga_IE.utf8@euro
 232 gl_ES
 233 gl_ES@euro
 234 gl_ES.utf8
 235 gl_ES.utf8@euro
 236 gv_GB
 237 gv_GB.utf8
 238 he_IL
 239 he_IL.utf8
 240 hi_IN
 241 hr_HR
 242 hr_HR.utf8
 243 hu_HU
 244 hu_HU.utf8
 245 id_ID
 246 id_ID.utf8
 247 is_IS
 248 is_IS.utf8
 249 it_CH
 250 it_CH.utf8
 251 it_IT
 252 it_IT@euro
 253 it_IT.utf8
 254 it_IT.utf8@euro
 255 iw_IL
 256 iw_IL.utf8
 257 ja_JP.eucjp
 258 ja_JP.utf8
 259 ka_GE
 260 kl_GL
 261 kl_GL.utf8
 262 ko_KR.euckr
 263 ko_KR.utf8
 264 kw_GB
 265 kw_GB.utf8
 266 lt_LT
 267 lt_LT.utf8
 268 lv_LV
 269 lv_LV.utf8
 270 mi_NZ
 271 mk_MK
 272 mk_MK.utf8
 273 mr_IN
 274 ms_MY
 275 ms_MY.utf8
 276 mt_MT
 277 mt_MT.utf8
 278 nl_BE
 279 nl_BE@euro
 280 nl_BE.utf8
 281 nl_BE.utf8@euro
 282 nl_NL
 283 nl_NL@euro
 284 nl_NL.utf8
 285 nl_NL.utf8@euro
 286 nn_NO
 287 nn_NO.utf8
 288 no_NO
 289 no_NO.utf8
 290 oc_FR
 291 pl_PL
 292 pl_PL.utf8
 293 POSIX
 294 pt_BR
 295 pt_BR.utf8
 296 pt_PT
 297 pt_PT@euro
 298 pt_PT.utf8
 299 pt_PT.utf8@euro
 300 ro_RO
 301 ro_RO.utf8
 302 ru_RU
 303 ru_RU.koi8r
 304 ru_RU.utf8
 305 ru_UA
 306 ru_UA.utf8
 307 se_NO
 308 sk_SK
 309 sk_SK.utf8
 310 sl_SI
 311 sl_SI.utf8
 312 sq_AL
 313 sq_AL.utf8
 314 sr_YU
 315 sr_YU@cyrillic
 316 sr_YU.utf8
 317 sr_YU.utf8@cyrillic
 318 sv_FI
 319 sv_FI@euro
 320 sv_FI.utf8
 321 sv_FI.utf8@euro
 322 sv_SE
 323 sv_SE.iso885915
 324 sv_SE.utf8
 325 ta_IN
 326 te_IN
 327 tg_TJ
 328 th_TH
 329 th_TH.utf8
 330 tl_PH
 331 tr_TR
 332 tr_TR.utf8
 333 uk_UA
 334 uk_UA.utf8
 335 ur_PK
 336 uz_UZ
 337 vi_VN
 338 vi_VN.tcvn
 339 wa_BE
 340 wa_BE@euro
 341 yi_US
 342 zh_CN
 343 zh_CN.gb18030
 344 zh_CN.gbk
 345 zh_CN.utf8
 346 zh_HK
 347 zh_HK.utf8
 348 zh_TW
 349 zh_TW.euctw
 350 zh_TW.utf8
 351 </pre></blockquote></div></li><li><p>
 352        <code class="code">`locale`</code> displays environmental variables that
 353        impact how locale("") will be deduced.
 354      </p><div class="blockquote"><blockquote class="blockquote"><pre class="programlisting">
 355 LANG=en_US
 356 LC_CTYPE="en_US"
 357 LC_NUMERIC="en_US"
 358 LC_TIME="en_US"
 359 LC_COLLATE="en_US"
 360 LC_MONETARY="en_US"
 361 LC_MESSAGES="en_US"
 362 LC_PAPER="en_US"
 363 LC_NAME="en_US"
 364 LC_ADDRESS="en_US"
 365 LC_TELEPHONE="en_US"
 366 LC_MEASUREMENT="en_US"
 367 LC_IDENTIFICATION="en_US"
 368 LC_ALL=
 369 </pre></blockquote></div></li></ul></div><p>
 370 From Josuttis, p. 697-698, which says, that "there is only *one*
 371 relation (of the C++ locale mechanism) to the C locale mechanism: the
 372 global C locale is modified if a named C++ locale object is set as the
 373 global locale" (emphasis Paolo), that is:
 374 </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>
 375   On the other hand, there is *no* vice versa, that is, calling
 376   setlocale has *no* whatsoever on the C++ locale mechanism, in
 377   particular on the working of locale(""), which constructs the locale
 378   object from the environment of the running program, that is, in
 379   practice, the set of LC_ALL, LANG, etc. variable of the shell.
 380 </p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.future"></a>Future</h3></div></div></div><div class="itemizedlist"><ul type="disc"><li><p>
 381        Locale initialization: at what point does _S_classic, _S_global
 382        get initialized? Can named locales assume this initialization
 383        has already taken place?
 384      </p></li><li><p>
 385        Document how named locales error check when filling data
 386        members. I.e., a fr_FR locale that doesn't have
 387        numpunct::truename(): does it use "true"? Or is it a blank
 388        string? What's the convention?
 389    </p></li><li><p>
 390        Explain how locale aliasing happens. When does "de_DE" use "de"
 391        information? What is the rule for locales composed of just an
 392        ISO language code (say, "de") and locales with both an ISO
 393        language code and ISO country code (say, "de_DE").
 394      </p></li><li><p>
 395        What should non-required facet instantiations do?  If the
 396        generic implementation is provided, then how to end-users
 397        provide specializations?
 398    </p></li></ul></div></div><div class="bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="locales.locale.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry"><a id="id412273"></a><p><span class="title"><i>
 399       The GNU C Library
 400     </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"><a id="id398173"></a><p><span class="title"><i>
 401       Correspondence
 402     </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"><a id="id427688"></a><p><span class="title"><i>
 403       ISO/IEC 14882:1998 Programming languages - C++
 404     </i>. </span><span class="copyright">Copyright © 1998 ISO. </span></p></div><div class="biblioentry"><a id="id427707"></a><p><span class="title"><i>
 405       ISO/IEC 9899:1999 Programming languages - C
 406     </i>. </span><span class="copyright">Copyright © 1999 ISO. </span></p></div><div class="biblioentry"><a id="id406617"></a><p><span class="title"><i>
 407       System Interface Definitions, Issue 6 (IEEE Std. 1003.1-200x)
 408     </i>. </span><span class="copyright">Copyright © 1999
 409       The Open Group/The Institute of Electrical and Electronics Engineers, Inc.. </span><span class="biblioid">
 410       <a class="ulink" href="http://www.opennc.org/austin/docreg.html" target="_top">
 411       </a>
 412     . </span></p></div><div class="biblioentry"><a id="id471678"></a><p><span class="title"><i>
 413       The C++ Programming Language, Special Edition
 414     </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">
 415         Addison Wesley
 416       . </span></span></p></div><div class="biblioentry"><a id="id414572"></a><p><span class="title"><i>
 417       Standard C++ IOStreams and Locales
 418     </i>. </span><span class="subtitle">
 419       Advanced Programmer's Guide and Reference
 420     . </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">
 421         Addison Wesley Longman
 422       . </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="bk01pt06ch15.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part VI. Localization </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>