libs/type_traits/doc/extent.qbk
[/ Copyright 2007 John Maddock. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt). ] [section:extent extent] template <class T, std::size_t N = 0> struct extent : public __integral_constant<std::size_t, EXTENT(T,N)> {}; __inherit Class template extent inherits from `__integral_constant<std::size_t, EXTENT(T,N)>`, where `EXTENT(T,N)` is the number of elements in the N'th array dimension of type `T`. If `T` is not a (built-in) array type, or if `N > __rank<T>::value`, or if the N'th array bound is incomplete, then `EXTENT(T,N)` is zero. __header ` #include <boost/type_traits/extent.hpp>` or ` #include <boost/type_traits.hpp>` __examples [:`extent<int[1]>` inherits from `__integral_constant<std::size_t, 1>`.] [:`extent<double[2][3][4], 0>::type` is the type `__integral_constant<std::size_t, 2>`.] [:`extent<double[2][3][4], 1>::type` is the type `__integral_constant<std::size_t, 3>`.] [:`extent<double[2][3][4], 3>::type` is the type `__integral_constant<std::size_t, 4>`.] [:`extent<int[4]>::value` is an integral constant expression that evaluates to /4/.] [:`extent<int[][2]>::value` is an integral constant expression that evaluates to /0/.] [:`extent<int[][2], 1>::value` is an integral constant expression that evaluates to /2/.] [:`extent<int*>::value` is an integral constant expression that evaluates to /0/.] [:`extent<boost::array<int, 3> >::value` is an integral constant expression that evaluates to /0/: `boost::array` is a class type and [*not an array type]!] [:`extent<T>::value_type` is the type `std::size_t`.] [endsect]