1 // (C) Copyright David Abrahams 2001. 2 // Distributed under the Boost Software License, Version 1.0. (See 3 // accompanying file LICENSE_1_0.txt or copy at 4 // http://www.boost.org/LICENSE_1_0.txt) 5 // 6 // See http://www.boost.org for most recent version including documentation. 7 8 // Revision History 9 // 09 Feb 01 Applied John Maddock's Borland patch Moving <true> 10 // specialization to unspecialized template (David Abrahams) 11 // 06 Feb 01 Created (David Abrahams) 12 13 #ifndef SELECT_TYPE_DWA20010206_HPP 14 # define SELECT_TYPE_DWA20010206_HPP 15 16 namespace boost { namespace detail { 17 18 // Template class if_true -- select among 2 types based on a bool constant expression 19 // Usage: 20 // typename if_true<(bool_const_expression)>::template then<true_type, false_type>::type 21 22 // HP aCC cannot deal with missing names for template value parameters 23 template <bool b> struct if_true 24 { 25 template <class T, class F> 26 struct then { typedef T type; }; 27 }; 28 29 template <> 30 struct if_true<false> 31 { 32 template <class T, class F> 33 struct then { typedef F type; }; 34 }; 35 }} 36 #endif // SELECT_TYPE_DWA20010206_HPP 37