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element<T>::type takes constness into consideration

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[SVN r17666]
This commit is contained in:
Jaakko Järvi
2003-02-26 23:10:55 +00:00
parent 496cc84960
commit 1972959fda
2 changed files with 18 additions and 1 deletions
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4
doc/tuple_advanced_interface.html
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@ -20,7 +20,9 @@ Suppose <code>T</code> is a tuple type, and <code>N</code> is a constant integra
<code><pre>element&lt;N, T&gt;::type</pre></code> <code><pre>element&lt;N, T&gt;::type</pre></code>
gives the type of the <code>N</code>th element in the tuple type <code>T</code>. gives the type of the <code>N</code>th element in the tuple type <code>T</code>. If <code>T</code> is const, the resulting type is const qualified as well.
Note that the constness of <code>T</code> does not affect reference type
elements.
</p> </p>
<code><pre>length&lt;T&gt;::value</pre></code> <code><pre>length&lt;T&gt;::value</pre></code>

15
include/boost/tuple/detail/tuple_basic.hpp
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@ -153,6 +153,21 @@ struct element<0,T>
typedef typename T::head_type type; typedef typename T::head_type type;
}; };
template<int N, class T>
struct element<N, const T>
{
private:
typedef typename T::tail_type Next;
typedef typename element<N-1, Next>::type unqualified_type;
public:
typedef typename boost::add_const<unqualified_type>::type type;
};
template<class T>
struct element<0,const T>
{
typedef typename boost::add_const<typename T::head_type>::type type;
};
// -get function templates ----------------------------------------------- // -get function templates -----------------------------------------------
// Usage: get<N>(aTuple) // Usage: get<N>(aTuple)