Home Explore Help
Register Sign In
devn00b
/
EQ2EMu
9
3
Fork 0
Files Issues 59
Tree: 9d9a5ec294
Branches Tags
EQ2EMu
/
EQ2
/
source
/
depends
/
boost_1_72_0
/
libs
/
optional
/
doc
/
html
/
boost_optional
/
dependencies_and_portability
/
emplace_operations_in_older_compilers.html

emplace_operations_in_older_compilers.html 11 KB
History Raw

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990 
  1. <html>
    2. 

  2. <head>
    3. 

  3. <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
    4. 

  4. <title>Emplace operations in older compilers</title>
    5. 

  5. <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
    6. 

  6. <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
    7. 

  7. <link rel="home" href="../../index.html" title="Boost.Optional">
    8. 

  8. <link rel="up" href="../dependencies_and_portability.html" title="Dependencies and Portability">
    9. 

  9. <link rel="prev" href="../dependencies_and_portability.html" title="Dependencies and Portability">
    10. 

  10. <link rel="next" href="optional_reference_binding.html" title="Optional Reference Binding">
    11. 

  11. </head>
    12. 

  12. <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
    13. 

  13. <table cellpadding="2" width="100%"><tr>
    14. 

  14. <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
    15. 

  15. <td align="center"><a href="../../../../../../index.html">Home</a></td>
    16. 

  16. <td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
    17. 

  17. <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
    18. 

  18. <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
    19. 

  19. <td align="center"><a href="../../../../../../more/index.htm">More</a></td>
    20. 

  20. </tr></table>
    21. 

  21. <hr>
    22. 

  22. <div class="spirit-nav">
    23. 

  23. <a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
    24. 

  24. </div>
    25. 

  25. <div class="section">
    26. 

  26. <div class="titlepage"><div><div><h3 class="title">
    27. 

  27. <a name="boost_optional.dependencies_and_portability.emplace_operations_in_older_compilers"></a><a class="link" href="emplace_operations_in_older_compilers.html" title="Emplace operations in older compilers">Emplace
    28. 

  28.       operations in older compilers</a>
    29. 

  29. </h3></div></div></div>
    30. 

  30. <p>
    31. 

  31.         <a name="optional_emplace_workaround"></a>Certain constructors and functions
    32. 

  32.         in the interface of <code class="computeroutput"><span class="identifier">optional</span></code>
    33. 

  33.         perform a 'perfect forwarding' of arguments:
    34. 

  34.       </p>
    35. 

  35. <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
    36. 

  36. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
    37. 

  37. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
    38. 

  38. </pre>
    39. 

  39. <p>
    40. 

  40.         On compilers that do not support variadic templates, each of these functions
    41. 

  41.         is substituted with two overloads, one forwarding a single argument, the
    42. 

  42.         other forwarding zero arguments. This forms the following set:
    43. 

  43.       </p>
    44. 

  44. <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    45. 

  45. <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">);</span>
    46. 

  46. 

  47. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    48. 

  48. <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">);</span>
    49. 

  49. 

  50. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    51. 

  51. <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">();</span>
    52. 

  52. </pre>
    53. 

  53. <p>
    54. 

  54.         On compilers that do not support rvalue references, each of these functions
    55. 

  55.         is substituted with three overloadss: taking <code class="computeroutput"><span class="keyword">const</span></code>
    56. 

  56.         and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference,
    57. 

  57.         and third forwarding zero arguments. This forms the following set:
    58. 

  58.       </p>
    59. 

  59. <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    60. 

  60. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    61. 

  61. <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">);</span>
    62. 

  62. 

  63. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    64. 

  64. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    65. 

  65. <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">);</span>
    66. 

  66. 

  67. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    68. 

  68. <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
    69. 

  69. <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">();</span>
    70. 

  70. </pre>
    71. 

  71. <p>
    72. 

  72.         This workaround addressess about 40% of all use cases. If this is insufficient,
    73. 

  73.         you need to resort to using <a class="link" href="../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
    74. 

  74.         Factories</a>.
    75. 

  75.       </p>
    76. 

  76. </div>
    77. 

  77. <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
    78. 

  78. <td align="left"></td>
    79. 

  79. <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 Andrzej Krzemie&#324;ski<p>
    80. 

  80.         Distributed under the Boost Software License, Version 1.0. (See accompanying
    81. 

  81.         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
    82. 

  82.       </p>
    83. 

  83. </div></td>
    84. 

  84. </tr></table>
    85. 

  85. <hr>
    86. 

  86. <div class="spirit-nav">
    87. 

  87. <a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
    88. 

  88. </div>
    89. 

  89. </body>
    90. 

  90. </html>
    91.