--- /dev/null
+// $Id$
+//
+// Copyright (C) 2007
+// Fraunhofer Institute for Open Communication Systems (FOKUS)
+// Competence Center NETwork research (NET), St. Augustin, GERMANY
+// Stefan Bund <g0dil@berlios.de>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the
+// Free Software Foundation, Inc.,
+// 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+/** \file
+ \brief mpl public header */
+
+#ifndef HH_SENF_Utils_mpl_
+#define HH_SENF_Utils_mpl_ 1
+
+// Custom includes
+#include "../config.hh"
+
+//#include "mpl.mpp"
+#include "mpl.ih"
+///////////////////////////////hh.p////////////////////////////////////////
+
+namespace senf {
+namespace mpl {
+
+ /** \defgroup senfmpl Template meta programming helpers
+ */
+
+ /** \brief Marker class for empty default values etc.
+
+ This is like Boosts \c boost::mpl::na just an empty class used as template default argument
+ to mark missing arguments
+
+ \note Don't use this as an empty base class. We may add some informative members to this.
+ \ingroup senfmpl
+ */
+ struct nil {};
+
+ /** \brief Return-value type used to implement overload selection
+
+ The senf::mpl::rv type is used together with \ref SENF_MPL_RV() to select template
+ specializations based on a set of overloads:
+
+ \code
+ template <unsigned _> struct select {};
+
+ // Case 0
+ template <>
+ struct select<0> {
+ static bool const has_int_value = true;
+ void frobble();
+ };
+ template <class T>
+ senf::mpl::rv<0> select_(int, senf::mpl::take_int<T::value> * = 0);
+
+ // Case 1
+ template <>
+ struct select<1> {
+ static bool const has_int_value = false;
+ void dazzle();
+ };
+ template <class T>
+ senf::mpl::rv<1> select_(...);
+
+ template <class T>
+ struct choice : public select<SENF_MPL_RV( select_<T>(0) )> {};
+
+ struct A { static const int value = 0; };
+ struct B {};
+
+ choice<A> a; a.frobble();
+ choice<B> b; b.dazzle();
+ \endcode
+
+ The selection is always based on two components: A selector class specialized for each of
+ the possible choices and an overloaded function (only signatures, no implementation needed)
+ to provide the conditions.
+
+ When instantiatinv <tt>choice<T></tt>, we forward \a T to the <tt>select_</tt> set of
+ overloads. Because of <a href="http://en.wikipedia.org/wiki/SFINAE">SFINAE</a>, the overload
+ set will only contain those instantiations, for which template expansion does not fail.
+
+ So, if \a T has an integer \c value member, both \c select_ overloads are ok and the call
+ <tt>select_<T>(0)</tt> will choose the first (case 0) variant, since the argument \c 0 is
+ better matched by \c int than by <tt>...</tt>.
+
+ However, if \a T does not have an integer \c value member, expansion for the first overload
+ fails and the overload set only contains the second case.
+
+ \ref SENF_MPL_RV() internally uses \c sizeof to find out, \e which overload was selected
+ and returns the senf::mpl::rv-argument of that overloads return type. For this to work, the
+ \c select_ functions need not be implemented since no code is generated and \c select_ is
+ never called.
+
+ This number is than forwarded as template argument to \c select which is specialized for
+ each case. Therefore, <tt>choice\<A\></tt> has a \c frobble() member whereas
+ <tt>choice\<B\></tt> has a \c dazzle() member.
+
+ \see \ref SENF_MPL_RV
+ \ingroup senfmpl
+ */
+ template <unsigned n>
+ struct rv {
+ char _[SENF_MPL_RV_ALIGNMENT][n+1];
+ };
+
+ /** \brief Get return value of overload selector
+
+ Used together with senf::mpl::rv to implement overload selection.
+
+ \see \ref senf::mpl::rv
+ \ingroup senfmpl
+ \hideinitializer
+ */
+# define SENF_MPL_RV(expr) (sizeof(expr)/SENF_MPL_RV_ALIGNMENT-1)
+
+ /** \brief Take an arbitrary unsigned integer template argument
+
+ Used together with <a href="http://en.wikipedia.org/wiki/SFINAE">SFINAE</a>: The expression
+ <tt>take_uint<</tt> \a expr <tt>></tt> is only valid if \a expr is valid and returns a value
+ convertible to an unsigned integer.
+
+ \ingroup senfmpl
+ */
+ template <unsigned long _> struct take_uint {};
+
+ /** \brief Take an arbitrary integer template argument
+
+ Used together with <a href="http://en.wikipedia.org/wiki/SFINAE">SFINAE</a>: The expression
+ <tt>take_int<</tt> \a expr <tt>></tt> is only valid if \a expr is valid and returns a value
+ convertible to an integer.
+
+ \ingroup senfmpl
+ */
+ template <long _> struct take_int {};
+
+ /** \brief Take an arbitrary type template argument
+
+ Used together with <a href="http://en.wikipedia.org/wiki/SFINAE">SFINAE</a>: The expression
+ <tt>take_class<</tt> \a expr <tt>></tt> is only valid if \a expr is valid and is a type.
+
+ \ingroup senfmpl
+ */
+ template <class _> struct take_class {};
+
+#ifndef SENF_MPL_SLOT_NOEXPAND
+
+ /** \brief Define MPL slot
+
+ The slot macros \ref SENF_MPL_SLOT_DEF(), \ref SENF_MPL_SLOT_SET() and \ref
+ SENF_MPL_SLOT_GET() provide a facility to get the last unsigned integer value assigned to
+ the slot before the current point in the current class.
+ \code
+ struct Foo
+ {
+ // Define SLOT slot named 'accum' initialized to 0
+ SENF_MPL_SLOT_DEF(accum, 0);
+
+ // Add 2 to 'accum'
+ SENF_MPL_SLOT_SET(accum, SENF_MPL_SLOT_GET(accum) + 2);
+
+ // Multiply 'accum' by 3
+ SENF_MPL_SLOT_SET(accum, SENF_MPL_SLOT_GET(accum) * 3);
+
+ // Define the result as a constant expression. result is now 6
+ static unsigned result = SENF_MPL_SLOT_GET(accum);
+ };
+ \endcode
+ Of course, it does not make sense to use these macros for simple arithmetic as in the
+ example. The SENF_MPL_SLOT macros allow to define macros which pass information from one
+ macro invocation to the next.
+
+ \implementation The implementation is based on __LINE__: We check backwards for a value
+ defined on a previous line. The check is limited to 80 lines backwards.
+
+ \ingroup senfmpl
+ \hideinitializer
+ */
+# define SENF_MPL_SLOT_DEF(name,value) \
+ template <class _> \
+ static senf::mpl::rv<0> _SENF_MPL_SLOT_ ## name (_); \
+ SENF_MPL_SLOT_SET(name,value)
+
+ /** \brief Define MPL slot initialized to 0
+
+ This is like \ref SENF_MPL_SLOT_DEF() but initializes the slot to the fixed value 0. The
+ advantage over \ref SENF_MPL_SLOT_DEF() is, that this macro may be called from an include
+ file whereas all the other \\c SENF_MPL_SLOT_ macros must always be called from the relevant
+ file.
+ */
+# define SENF_MPL_SLOT_DEF_ZERO(name) \
+ template <class _> \
+ static senf::mpl::rv<0> _SENF_MPL_SLOT_ ## name (_);
+
+ /** \brief Set MPL slot
+ \see \ref SENF_MPL_SLOT_DEF()
+ \ingroup senfmpl
+ \hideinitializer
+ */
+# define SENF_MPL_SLOT_SET(name,value) \
+ static senf::mpl::rv<unsigned(value)+1> \
+ _SENF_MPL_SLOT_ ## name (senf::mpl::take_int<__LINE__>)
+
+ /** \brief Get current MPL slot value
+ \see \ref SENF_MPL_SLOT_DEF()
+ \ingroup senfmpl
+ \hideinitializer
+ */
+# define SENF_MPL_SLOT_GET(name) \
+ SENF_MPL_SLOT_I_GET(name)
+
+#endif
+
+}}
+
+///////////////////////////////hh.e////////////////////////////////////////
+//#include "mpl.cci"
+//#include "mpl.ct"
+//#include "mpl.cti"
+#endif
+
+\f
+// Local Variables:
+// mode: c++
+// fill-column: 100
+// comment-column: 40
+// c-file-style: "senf"
+// indent-tabs-mode: nil
+// ispell-local-dictionary: "american"
+// compile-command: "scons -u test"
+// End:
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