Update of /cvsroot/boost/boost/boost/pending
In directory sc8-pr-cvs3.sourceforge.net:/tmp/cvs-serv19760
Modified Files:
ct_if.hpp
Log Message:
Replaced the implementation of ct_if with a facade implementation that
defers to Boost.MPL.
Index: ct_if.hpp
===================================================================
RCS file: /cvsroot/boost/boost/boost/pending/ct_if.hpp,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -d -r1.6 -r1.7
--- ct_if.hpp 30 Jan 2005 15:47:46 -0000 1.6
+++ ct_if.hpp 13 Nov 2006 15:35:54 -0000 1.7
@@ -3,107 +3,39 @@
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
-// The ct_if implementation that avoids partial specialization is
-// based on the IF class by Ulrich W. Eisenecker and Krzysztof
-// Czarnecki.
+// This header replaces the implementation of ct_if that preceded the
+// introduction of Boost.MPL with a facade that defers to that reviewed and
+// accepted library.
+
+// Author: Ronald Garcia
+// Date: 20 October, 2006
+
#ifndef BOOST_CT_IF_HPP
#define BOOST_CT_IF_HPP
-#include <boost/config.hpp>
-/*
- There is a bug in the Borland compiler with regards to using
- integers to specialize templates. This made it hard to use ct_if in
- the graph library. Changing from 'ct_if' to 'ct_if_t' fixed the
- problem.
-*/
+// A stub implementation in terms of Boost.MPL
-#include <boost/type_traits/integral_constant.hpp> // true_type and false_type
+#include <boost/mpl/if.hpp>
+#include <boost/mpl/not.hpp>
+#include <boost/mpl/and.hpp>
+// true_type and false_type are used by applications of ct_if
+#include <boost/type_traits/integral_constant.hpp>
namespace boost {
- struct ct_if_error { };
-
template <class A, class B>
- struct ct_and { typedef false_type type; };
- template <> struct ct_and<true_type,true_type> { typedef true_type type; };
-
- template <class A> struct ct_not { typedef ct_if_error type; };
- template <> struct ct_not<true_type> { typedef false_type type; };
- template <> struct ct_not<false_type> { typedef true_type type; };
+ struct ct_and : boost::mpl::and_<A,B> {};
-#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
+ template <class A>
+ struct ct_not : mpl::not_<A> {};
-// agurt, 15/sep/02: in certain cases Borland has problems with
-// choosing the right 'ct_if' specialization even though 'cond'
-// _does_ equal '1'; the easiest way to fix it is to make first
-// 'ct_if' non-type template parameter boolean.
-#if !defined(__BORLANDC__)
template <bool cond, class A, class B>
- struct ct_if { typedef ct_if_error type; };
- template <class A, class B>
- struct ct_if<true, A, B> { typedef A type; };
- template <class A, class B>
- struct ct_if<false, A, B> { typedef B type; };
-#else
- template <bool cond, class A, class B>
- struct ct_if { typedef A type; };
- template <class A, class B>
- struct ct_if<false, A, B> { typedef B type; };
-#endif
-
- template <class cond, class A, class B>
- struct ct_if_t { typedef ct_if_error type; };
- template <class A, class B>
- struct ct_if_t<true_type, A, B> { typedef A type; };
- template <class A, class B>
- struct ct_if_t<false_type, A, B> { typedef B type; };
-
-#else
-
- namespace detail {
-
- template <int condition, class A, class B> struct IF;
- template <int condition> struct SlectSelector;
- struct SelectFirstType;
- struct SelectSecondType;
-
- struct SelectFirstType {
- template<class A, class B>
- struct Template { typedef A type; };
- };
-
- struct SelectSecondType {
- template<class A, class B>
- struct Template { typedef B type; };
- };
-
- template<int condition>
- struct SlectSelector {
- typedef SelectFirstType type;
- };
-
- template <>
- struct SlectSelector<0> {
- typedef SelectSecondType type;
- };
+ struct ct_if : mpl::if_c<cond,A,B> {};
- } // namespace detail
-
- template<int condition, class A, class B>
- struct ct_if
- {
- typedef typename detail::SlectSelector<condition>::type Selector;
- typedef typename Selector::template Template<A, B>::type type;
- };
-
template <class cond, class A, class B>
- struct ct_if_t {
- typedef typename ct_if<cond::value, A, B>::type type;
- };
-
-#endif
+ struct ct_if_t : mpl::if_<cond,A,B> {};
} // namespace boost
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