// This file is part of Eigen, a lightweight C++ template library // for linear algebra. // // Copyright (C) 2017 Gael Guennebaud <[email protected]> // // 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 // IWYU pragma: private #include "../InternalHeaderCheck.h" namespace Eigen { namespace internal { template <int N> class FixedInt; template <int N> class VariableAndFixedInt; /** \internal * \class FixedInt * * This class embeds a compile-time integer \c N. * * It is similar to c++11 std::integral_constant<int,N> but with some additional features * such as: * - implicit conversion to int * - arithmetic and some bitwise operators: -, +, *, /, %, &, | * - c++98/14 compatibility with fix<N> and fix<N>() syntax to define integral constants. * * It is strongly discouraged to directly deal with this class FixedInt. Instances are expected to * be created by the user using Eigen::fix<N> or Eigen::fix<N>(). * \code * internal::cleanup_index_type<T>::type * internal::cleanup_index_type<T,DynamicKey>::type * \endcode * where T can a FixedInt<N>, a pointer to function FixedInt<N> (*)(), or numerous other integer-like representations. * \c DynamicKey is either Dynamic (default) or DynamicIndex and used to identify true compile-time values. * * For convenience, you can extract the compile-time value \c N in a generic way using the following helper: * \code * internal::get_fixed_value<T,DefaultVal>::value * \endcode * that will give you \c N if T equals FixedInt<N> or FixedInt<N> (*)(), and \c DefaultVal if T does not embed any * compile-time value (e.g., T==int). * * \sa fix<N>, class VariableAndFixedInt */ template <int N> class FixedInt { … }; /** \internal * \class VariableAndFixedInt * * This class embeds both a compile-time integer \c N and a runtime integer. * Both values are supposed to be equal unless the compile-time value \c N has a special * value meaning that the runtime-value should be used. Depending on the context, this special * value can be either Eigen::Dynamic (for positive quantities) or Eigen::DynamicIndex (for * quantities that can be negative). * * It is the return-type of the function Eigen::fix<N>(int), and most of the time this is the only * way it is used. It is strongly discouraged to directly deal with instances of VariableAndFixedInt. * Indeed, in order to write generic code, it is the responsibility of the callee to properly convert * it to either a true compile-time quantity (i.e. a FixedInt<N>), or to a runtime quantity (e.g., an Index) * using the following generic helper: * \code * internal::cleanup_index_type<T>::type * internal::cleanup_index_type<T,DynamicKey>::type * \endcode * where T can be a template instantiation of VariableAndFixedInt or numerous other integer-like representations. * \c DynamicKey is either Dynamic (default) or DynamicIndex and used to identify true compile-time values. * * For convenience, you can also extract the compile-time value \c N using the following helper: * \code * internal::get_fixed_value<T,DefaultVal>::value * \endcode * that will give you \c N if T equals VariableAndFixedInt<N>, and \c DefaultVal if T does not embed any compile-time * value (e.g., T==int). * * \sa fix<N>(int), class FixedInt */ template <int N> class VariableAndFixedInt { … }; template <typename T, int Default = Dynamic> struct get_fixed_value { … }; get_fixed_value<FixedInt<N>, Default>; get_fixed_value<VariableAndFixedInt<N>, Default>; get_fixed_value<variable_if_dynamic<T, N>, Default>; template <typename T> EIGEN_DEVICE_FUNC Index get_runtime_value(const T &x) { … } // Cleanup integer/FixedInt/VariableAndFixedInt/etc types: // By default, no cleanup: template <typename T, int DynamicKey = Dynamic, typename EnableIf = void> struct cleanup_index_type { … }; // Convert any integral type (e.g., short, int, unsigned int, etc.) to Eigen::Index cleanup_index_type<T, DynamicKey, std::enable_if_t<internal::is_integral<T>::value>>; // If VariableAndFixedInt does not match DynamicKey, then we turn it to a pure compile-time value: cleanup_index_type<VariableAndFixedInt<N>, DynamicKey>; // If VariableAndFixedInt matches DynamicKey, then we turn it to a pure runtime-value (aka Index): cleanup_index_type<VariableAndFixedInt<DynamicKey>, DynamicKey>; cleanup_index_type<std::integral_constant<int, N>, DynamicKey>; } // end namespace internal #ifndef EIGEN_PARSED_BY_DOXYGEN fix; #else // EIGEN_PARSED_BY_DOXYGEN /** \var fix<N>() * \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 * * See also the function fix(int) to pass both a compile-time and runtime value. * * In c++14, it is implemented as: * \code * template<int N> static const internal::FixedInt<N> fix{}; * \endcode * where internal::FixedInt<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::FixedInt<N>. * * \sa fix<N>(int), seq, seqN */ template <int N> static const auto fix(); /** \fn fix<N>(int) * \ingroup Core_Module * * This function returns an object embedding both a compile-time integer \c N, and a fallback runtime value \a val. * * \tparam N the compile-time integer value * \param val the fallback runtime integer value * * This function is a more general version of the \ref fix identifier/function that can be used in template code * where the compile-time value could turn out to actually mean "undefined at compile-time". For positive integers * such as a size or a dimension, this case is identified by Eigen::Dynamic, whereas runtime signed integers * (e.g., an increment/stride) are identified as Eigen::DynamicIndex. In such a case, the runtime value \a val * will be used as a fallback. * * A typical use case would be: * \code * template<typename Derived> void foo(const MatrixBase<Derived> &mat) { * const int N = Derived::RowsAtCompileTime==Dynamic ? Dynamic : Derived::RowsAtCompileTime/2; * const int n = mat.rows()/2; * ... mat( seqN(0,fix<N>(n) ) ...; * } * \endcode * In this example, the function Eigen::seqN knows that the second argument is expected to be a size. * If the passed compile-time value N equals Eigen::Dynamic, then the proxy object returned by fix will be dissmissed, * and converted to an Eigen::Index of value \c n. Otherwise, the runtime-value \c n will be dissmissed, and the * returned ArithmeticSequence will be of the exact same type as <tt> seqN(0,fix<N>) </tt>. * * \sa fix, seqN, class ArithmeticSequence */ template <int N> static const auto fix(int val); #endif // EIGEN_PARSED_BY_DOXYGEN } // end namespace Eigen #endif // EIGEN_INTEGRAL_CONSTANT_H
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