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| author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
|---|---|---|
| committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
| commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
| tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libstdc++-v3/doc/html/manual/pairs.html | |
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Diffstat (limited to 'libstdc++-v3/doc/html/manual/pairs.html')
| -rw-r--r-- | libstdc++-v3/doc/html/manual/pairs.html | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/libstdc++-v3/doc/html/manual/pairs.html b/libstdc++-v3/doc/html/manual/pairs.html new file mode 100644 index 000000000..8c4dbb763 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/pairs.html @@ -0,0 +1,45 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Pairs</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="utilities.html" title="Chapter 6. Utilities"/><link rel="prev" href="utilities.html" title="Chapter 6. Utilities"/><link rel="next" href="memory.html" title="Memory"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Pairs</th></tr><tr><td align="left"><a accesskey="p" href="utilities.html">Prev</a> </td><th width="60%" align="center">Chapter 6. + Utilities + +</th><td align="right"> <a accesskey="n" href="memory.html">Next</a></td></tr></table><hr/></div><div class="section" title="Pairs"><div class="titlepage"><div><div><h2 class="title"><a id="std.util.pairs"/>Pairs</h2></div></div></div><p>The <code class="code">pair<T1,T2></code> is a simple and handy way to + carry around a pair of objects. One is of type T1, and another of + type T2; they may be the same type, but you don't get anything + extra if they are. The two members can be accessed directly, as + <code class="code">.first</code> and <code class="code">.second</code>. + </p><p>Construction is simple. The default ctor initializes each member + with its respective default ctor. The other simple ctor, + </p><pre class="programlisting"> + pair (const T1& x, const T2& y); + </pre><p>does what you think it does, <code class="code">first</code> getting <code class="code">x</code> + and <code class="code">second</code> getting <code class="code">y</code>. + </p><p>There is a copy constructor, but it requires that your compiler + handle member function templates: + </p><pre class="programlisting"> + template <class U, class V> pair (const pair<U,V>& p); + </pre><p>The compiler will convert as necessary from U to T1 and from + V to T2 in order to perform the respective initializations. + </p><p>The comparison operators are done for you. Equality + of two <code class="code">pair<T1,T2></code>s is defined as both <code class="code">first</code> + members comparing equal and both <code class="code">second</code> members comparing + equal; this simply delegates responsibility to the respective + <code class="code">operator==</code> functions (for types like MyClass) or builtin + comparisons (for types like int, char, etc). + </p><p> + The less-than operator is a bit odd the first time you see it. It + is defined as evaluating to: + </p><pre class="programlisting"> + x.first < y.first || + ( !(y.first < x.first) && x.second < y.second ) + </pre><p>The other operators are not defined using the <code class="code">rel_ops</code> + functions above, but their semantics are the same. + </p><p>Finally, there is a template function called <code class="function">make_pair</code> + that takes two references-to-const objects and returns an + instance of a pair instantiated on their respective types: + </p><pre class="programlisting"> + pair<int,MyClass> p = make_pair(4,myobject); + </pre></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="utilities.html">Prev</a> </td><td align="center"><a accesskey="u" href="utilities.html">Up</a></td><td align="right"> <a accesskey="n" href="memory.html">Next</a></td></tr><tr><td align="left" valign="top">Chapter 6. + Utilities + + </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Memory</td></tr></table></div></body></html> |