projects / ceph.git / blame
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| 7c673cae FG |
1 | <?xml version="1.0" encoding="utf-8"?> |
| 2 | <!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" | |
| 3 | "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd"> | |
| 4 | <!-- | |
| 5 | Copyright 2013-20014, Antony Polukhin. | |
| 6 | ||
| 7 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 8 | file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
| 9 | --> | |
| 10 | <header name="boost/variant/polymorphic_get.hpp"> | |
| 11 | <namespace name="boost"> | |
| 12 | ||
| 13 | <class name="bad_polymorphic_get"> | |
| 14 | <inherit access="public"> | |
| 15 | <classname>boost::bad_get</classname> | |
| 16 | </inherit> | |
| 17 | ||
| 18 | <purpose> | |
| 19 | <simpara>The exception thrown in the event of a failed application of | |
| 20 | <code><functionname>boost::polymorphic_get</functionname></code> on the given | |
| 21 | operand value.</simpara> | |
| 22 | </purpose> | |
| 23 | ||
| 24 | <method name="what" specifiers="virtual" cv="const"> | |
| 25 | <type>const char *</type> | |
| 26 | </method> | |
| 27 | </class> | |
| 28 | ||
| 29 | <overloaded-function name="polymorphic_relaxed_get"> | |
| 30 | <signature> | |
| 31 | <template> | |
| 32 | <template-type-parameter name="U"/> | |
| 33 | <template-type-parameter name="T1"/> | |
| 34 | <template-type-parameter name="T2"/> | |
| 35 | <template-varargs/> | |
| 36 | <template-type-parameter name="TN"/> | |
| 37 | </template> | |
| 38 | ||
| 39 | <type>U *</type> | |
| 40 | ||
| 41 | <parameter name="operand"> | |
| 42 | <paramtype><classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 43 | </parameter> | |
| 44 | </signature> | |
| 45 | ||
| 46 | <signature> | |
| 47 | <template> | |
| 48 | <template-type-parameter name="U"/> | |
| 49 | <template-type-parameter name="T1"/> | |
| 50 | <template-type-parameter name="T2"/> | |
| 51 | <template-varargs/> | |
| 52 | <template-type-parameter name="TN"/> | |
| 53 | </template> | |
| 54 | ||
| 55 | <type>const U *</type> | |
| 56 | ||
| 57 | <parameter name="operand"> | |
| 58 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 59 | </parameter> | |
| 60 | </signature> | |
| 61 | ||
| 62 | <signature> | |
| 63 | <template> | |
| 64 | <template-type-parameter name="U"/> | |
| 65 | <template-type-parameter name="T1"/> | |
| 66 | <template-type-parameter name="T2"/> | |
| 67 | <template-varargs/> | |
| 68 | <template-type-parameter name="TN"/> | |
| 69 | </template> | |
| 70 | ||
| 71 | <type>U &</type> | |
| 72 | ||
| 73 | <parameter name="operand"> | |
| 74 | <paramtype><classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 75 | </parameter> | |
| 76 | </signature> | |
| 77 | ||
| 78 | <signature> | |
| 79 | <template> | |
| 80 | <template-type-parameter name="U"/> | |
| 81 | <template-type-parameter name="T1"/> | |
| 82 | <template-type-parameter name="T2"/> | |
| 83 | <template-varargs/> | |
| 84 | <template-type-parameter name="TN"/> | |
| 85 | </template> | |
| 86 | ||
| 87 | <type>const U &</type> | |
| 88 | ||
| 89 | <parameter name="operand"> | |
| 90 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 91 | </parameter> | |
| 92 | </signature> | |
| 93 | ||
| 94 | <purpose> | |
| 95 | <simpara>Retrieves a value of a specified type from a given | |
| 96 | <code><classname>variant</classname></code>.</simpara> | |
| 97 | <simpara>Unlike <functionname>polymorphic_strict_get</functionname> does not assert at compile time | |
| 98 | that type <code>U</code> is one of the types that can be stored in variant.</simpara> | |
| 99 | </purpose> | |
| 100 | ||
| 101 | <description> | |
| 102 | <simpara>The <code>polymorphic_get</code> function allows run-time checked, | |
| 103 | type-safe retrieval of the content of the given | |
| 104 | <code><classname>variant</classname></code>. The function succeeds | |
| 105 | only if the content is of the specified type <code>U</code> or of type | |
| 106 | derived from type <code>U</code>, with | |
| 107 | failure indicated as described below.</simpara> | |
| 108 | <simpara><emphasis role="bold">Recomendation</emphasis>: Use | |
| 109 | <functionname>polymorphic_get</functionname> or <functionname>polymorphic_strict_get</functionname> | |
| 110 | in new code. | |
| 111 | <functionname>polymorphic_strict_get</functionname> | |
| 112 | provides more compile time checks and its behavior is closer to <code>std::get</code> | |
| 113 | from C++ Standard Library.</simpara> | |
| 114 | <simpara><emphasis role="bold">Warning</emphasis>: After either | |
| 115 | <code>operand</code> or its content is destroyed (e.g., when the | |
| 116 | given <code><classname>variant</classname></code> is assigned a | |
| 117 | value of different type), the returned reference is invalidated. | |
| 118 | Thus, significant care and caution must be extended when handling | |
| 119 | the returned reference.</simpara> | |
| 120 | </description> | |
| 121 | ||
| 122 | <notes> | |
| 123 | <simpara>As part of its guarantee of type-safety, <code>polymorphic_get</code> | |
| 124 | enforces <code>const</code>-correctness. Thus, the specified type | |
| 125 | <code>U</code> must be <code>const</code>-qualified whenever | |
| 126 | <code>operand</code> or its content is likewise | |
| 127 | <code>const</code>-qualified. The converse, however, is not required: | |
| 128 | that is, the specified type <code>U</code> may be | |
| 129 | <code>const</code>-qualified even when <code>operand</code> and its | |
| 130 | content are not.</simpara> | |
| 131 | </notes> | |
| 132 | ||
| 133 | <returns> | |
| 134 | <simpara>If passed a pointer, <code>polymorphic_get</code> returns a pointer to | |
| 135 | the value content if it is of the specified type <code>U</code> or of type | |
| 136 | derived from type <code>U</code>; | |
| 137 | otherwise, a null pointer is returned. If passed a reference, | |
| 138 | <code>polymorphic_get</code> returns a reference to the value content if it is of | |
| 139 | the specified type <code>U</code> or of type | |
| 140 | derived from type <code>U</code>; otherwise, an exception is thrown | |
| 141 | (see below).</simpara> | |
| 142 | </returns> | |
| 143 | ||
| 144 | <throws> | |
| 145 | <simpara>Overloads taking a | |
| 146 | <code><classname>variant</classname></code> pointer will not | |
| 147 | throw; the overloads taking a | |
| 148 | <code><classname>variant</classname></code> reference throw | |
| 149 | <code><classname>bad_polymorphic_get</classname></code> if the content is not of | |
| 150 | the specified type <code>U</code>or of type | |
| 151 | derived from type <code>U</code>.</simpara> | |
| 152 | </throws> | |
| 153 | ||
| 154 | <rationale> | |
| 155 | <simpara>While visitation via | |
| 156 | <code><functionname>apply_visitor</functionname></code> | |
| 157 | is generally preferred due to its greater safety, <code>polymorphic_get</code> may | |
| 158 | may be more convenient in some cases due to its straightforward | |
| 159 | usage.</simpara> | |
| 160 | </rationale> | |
| 161 | </overloaded-function> | |
| 162 | ||
| 163 | ||
| 164 | ||
| 165 | <overloaded-function name="polymorphic_strict_get"> | |
| 166 | <signature> | |
| 167 | <template> | |
| 168 | <template-type-parameter name="U"/> | |
| 169 | <template-type-parameter name="T1"/> | |
| 170 | <template-type-parameter name="T2"/> | |
| 171 | <template-varargs/> | |
| 172 | <template-type-parameter name="TN"/> | |
| 173 | </template> | |
| 174 | ||
| 175 | <type>U *</type> | |
| 176 | ||
| 177 | <parameter name="operand"> | |
| 178 | <paramtype><classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 179 | </parameter> | |
| 180 | </signature> | |
| 181 | ||
| 182 | <signature> | |
| 183 | <template> | |
| 184 | <template-type-parameter name="U"/> | |
| 185 | <template-type-parameter name="T1"/> | |
| 186 | <template-type-parameter name="T2"/> | |
| 187 | <template-varargs/> | |
| 188 | <template-type-parameter name="TN"/> | |
| 189 | </template> | |
| 190 | ||
| 191 | <type>const U *</type> | |
| 192 | ||
| 193 | <parameter name="operand"> | |
| 194 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 195 | </parameter> | |
| 196 | </signature> | |
| 197 | ||
| 198 | <signature> | |
| 199 | <template> | |
| 200 | <template-type-parameter name="U"/> | |
| 201 | <template-type-parameter name="T1"/> | |
| 202 | <template-type-parameter name="T2"/> | |
| 203 | <template-varargs/> | |
| 204 | <template-type-parameter name="TN"/> | |
| 205 | </template> | |
| 206 | ||
| 207 | <type>U &</type> | |
| 208 | ||
| 209 | <parameter name="operand"> | |
| 210 | <paramtype><classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 211 | </parameter> | |
| 212 | </signature> | |
| 213 | ||
| 214 | <signature> | |
| 215 | <template> | |
| 216 | <template-type-parameter name="U"/> | |
| 217 | <template-type-parameter name="T1"/> | |
| 218 | <template-type-parameter name="T2"/> | |
| 219 | <template-varargs/> | |
| 220 | <template-type-parameter name="TN"/> | |
| 221 | </template> | |
| 222 | ||
| 223 | <type>const U &</type> | |
| 224 | ||
| 225 | <parameter name="operand"> | |
| 226 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 227 | </parameter> | |
| 228 | </signature> | |
| 229 | ||
| 230 | <purpose> | |
| 231 | <simpara>Retrieves a value of a specified type from a given | |
| 232 | <code><classname>variant</classname></code>.</simpara> | |
| 233 | </purpose> | |
| 234 | ||
| 235 | <description> | |
| 236 | <simpara>Acts exactly like <functionname>polymorphic_relaxed_get</functionname> but does a compile time check | |
| 237 | that type <code>U</code> is one of the types that can be stored in variant.</simpara> | |
| 238 | </description> | |
| 239 | </overloaded-function> | |
| 240 | ||
| 241 | <overloaded-function name="polymorphic_get"> | |
| 242 | <signature> | |
| 243 | <template> | |
| 244 | <template-type-parameter name="U"/> | |
| 245 | <template-type-parameter name="T1"/> | |
| 246 | <template-type-parameter name="T2"/> | |
| 247 | <template-varargs/> | |
| 248 | <template-type-parameter name="TN"/> | |
| 249 | </template> | |
| 250 | ||
| 251 | <type>U *</type> | |
| 252 | ||
| 253 | <parameter name="operand"> | |
| 254 | <paramtype><classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 255 | </parameter> | |
| 256 | </signature> | |
| 257 | ||
| 258 | <signature> | |
| 259 | <template> | |
| 260 | <template-type-parameter name="U"/> | |
| 261 | <template-type-parameter name="T1"/> | |
| 262 | <template-type-parameter name="T2"/> | |
| 263 | <template-varargs/> | |
| 264 | <template-type-parameter name="TN"/> | |
| 265 | </template> | |
| 266 | ||
| 267 | <type>const U *</type> | |
| 268 | ||
| 269 | <parameter name="operand"> | |
| 270 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> *</paramtype> | |
| 271 | </parameter> | |
| 272 | </signature> | |
| 273 | ||
| 274 | <signature> | |
| 275 | <template> | |
| 276 | <template-type-parameter name="U"/> | |
| 277 | <template-type-parameter name="T1"/> | |
| 278 | <template-type-parameter name="T2"/> | |
| 279 | <template-varargs/> | |
| 280 | <template-type-parameter name="TN"/> | |
| 281 | </template> | |
| 282 | ||
| 283 | <type>U &</type> | |
| 284 | ||
| 285 | <parameter name="operand"> | |
| 286 | <paramtype><classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 287 | </parameter> | |
| 288 | </signature> | |
| 289 | ||
| 290 | <signature> | |
| 291 | <template> | |
| 292 | <template-type-parameter name="U"/> | |
| 293 | <template-type-parameter name="T1"/> | |
| 294 | <template-type-parameter name="T2"/> | |
| 295 | <template-varargs/> | |
| 296 | <template-type-parameter name="TN"/> | |
| 297 | </template> | |
| 298 | ||
| 299 | <type>const U &</type> | |
| 300 | ||
| 301 | <parameter name="operand"> | |
| 302 | <paramtype>const <classname>variant</classname><T1, T2, ..., TN> &</paramtype> | |
| 303 | </parameter> | |
| 304 | </signature> | |
| 305 | ||
| 306 | <purpose> | |
| 307 | <simpara>Retrieves a value of a specified type from a given | |
| 308 | <code><classname>variant</classname></code>.</simpara> | |
| 309 | </purpose> | |
| 310 | ||
| 311 | <description> | |
| 312 | <simpara>Evaluates to <functionname>polymorphic_strict_get</functionname> | |
| 313 | if <code>BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT</code> | |
| 314 | is not defined. If <code>BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT</code> | |
| 315 | is defined then evaluates to <functionname>polymorphic_relaxed_get</functionname>. </simpara> | |
| 316 | ||
| 317 | <simpara><emphasis role="bold">Recomendation</emphasis>: Use | |
| 318 | <functionname>polymorphic_get</functionname> in new code without defining | |
| 319 | <code>BOOST_VARIANT_USE_RELAXED_GET_BY_DEFAULT</code>. In that way | |
| 320 | <functionname>polymorphic_get</functionname> | |
| 321 | provides more compile time checks and its behavior is closer to <code>std::get</code> | |
| 322 | from C++ Standard Library.</simpara> | |
| 323 | </description> | |
| 324 | </overloaded-function> | |
| 325 | </namespace> | |
| 326 | </header> |