Move fix and symbolic to their own file, and improve doxygen compatibility

Eigen/src/Core/util/IntegralConstant.h

@@ -0,0 +1,87 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2017 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+#ifndef EIGEN_INTEGRAL_CONSTANT_H
+#define EIGEN_INTEGRAL_CONSTANT_H
+
+namespace Eigen {
+
+namespace internal {
+
+template<int N> struct fix_t {
+  static const int value = N;
+  operator int() const { return value; }
+  fix_t (fix_t<N> (*)() ) {}
+  fix_t() {}
+  // Needed in C++14 to allow fix<N>():
+  fix_t operator() () const { return *this; }
+};
+
+template<typename T, int Default=Dynamic> struct get_compile_time {
+  enum { value = Default };
+};
+
+template<int N,int Default> struct get_compile_time<fix_t<N>,Default> {
+  enum { value = N };
+};
+
+template<typename T> struct is_compile_time       { enum { value = false }; };
+template<int N> struct is_compile_time<fix_t<N> > { enum { value = true }; };
+
+} // end namespace internal
+
+#ifndef EIGEN_PARSED_BY_DOXYGEN
+
+#if __cplusplus > 201103L
+template<int N>
+static const internal::fix_t<N> fix{};
+#else
+template<int N>
+inline internal::fix_t<N> fix() { return internal::fix_t<N>(); }
+#endif
+
+#else // EIGEN_PARSED_BY_DOXYGEN
+
+/** \var fix
+  * \ingroup Core_Module
+  *
+  * This \em identifier permits to construct an object embedding a compile-time integer \c N.
+  *
+  * \tparam N the compile-time integer value
+  *
+  * It is typically used in conjunction with the Eigen::seq and Eigen::seqN functions to pass compile-time values to them:
+  * \code
+  * seqN(10,fix<4>,fix<-3>)   // <=> [10 7 4 1]
+  * \endcode
+  *
+  * In c++14, it is implemented as:
+  * \code
+  * template<int N> static const internal::fix_t<N> fix{};
+  * \endcode
+  * where internal::fix_t<N> is an internal template class similar to
+  * <a href="http://en.cppreference.com/w/cpp/types/integral_constant">\c std::integral_constant </a><tt> <int,N> </tt>
+  * Here, \c fix<N> is thus an object of type \c internal::fix_t<N>.
+  *
+  * In c++98/11, it is implemented as a function:
+  * \code
+  * template<int N> inline internal::fix_t<N> fix();
+  * \endcode
+  * Here internal::fix_t<N> is thus a pointer to function.
+  *
+  * If for some reason you want a true object in c++98 then you can write: \code fix<N>() \endcode which is also valid in c++14.
+  */
+template<int N>
+static const auto fix;
+
+#endif // EIGEN_PARSED_BY_DOXYGEN
+
+} // end namespace Eigen
+
+#endif // EIGEN_INTEGRAL_CONSTANT_H