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Sacado_mpl_has_type.hpp
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1// @HEADER
2// ***********************************************************************
3//
4// Sacado Package
5// Copyright (2006) Sandia Corporation
6//
7// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
8// the U.S. Government retains certain rights in this software.
9//
10// This library is free software; you can redistribute it and/or modify
11// it under the terms of the GNU Lesser General Public License as
12// published by the Free Software Foundation; either version 2.1 of the
13// License, or (at your option) any later version.
14//
15// This library is distributed in the hope that it will be useful, but
16// WITHOUT ANY WARRANTY; without even the implied warranty of
17// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18// Lesser General Public License for more details.
19//
20// You should have received a copy of the GNU Lesser General Public
21// License along with this library; if not, write to the Free Software
22// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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24// Questions? Contact David M. Gay (dmgay@sandia.gov) or Eric T. Phipps
25// (etphipp@sandia.gov).
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28// @HEADER
29
30#ifndef SACADO_MPL_HAS_TYPE_HPP
31#define SACADO_MPL_HAS_TYPE_HPP
32
33namespace Sacado {
34
35 namespace mpl {
36
37 // Uses SFINAE to determine if a type has a nested typedef called "type",
38 // i.e., whether the type is a metafunction
39
40 typedef char NotFound; // sizeof(NotFound) == 1
41 struct Found { char x[2]; }; // sizeof(Found) == 2
42
43 // Overload matches if and only if T::type exists
44 template <class T> Found testHasType(typename T::type*);
45
46 // Compiler prefers anything at all over ...
47 template <class T> NotFound testHasType(...);
48
49 template <class T> struct has_type {
50 static const bool value = (sizeof(testHasType<T>(0)) == sizeof(Found));
51 };
52
53 } // namespace mpl
54
55} // namespace Sacado
56
57#endif // SACADO_MPL_HAS_TYPE_HPP
Found testHasType(typename T::type *)