ThePEG/Config/TemplateTools.h

0001 // -*- C++ -*-
0002 //
0003 // TemplateTools.h is a part of ThePEG - Toolkit for HEP Event Generation
0004 // Copyright (C) 2006-2019 David Grellscheid, Leif Lonnblad
0005 //
0006 // ThePEG is licenced under version 3 of the GPL, see COPYING for details.
0007 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
0008 //
0009 #ifndef Template_Tools_H
0010 #define Template_Tools_H
0011
0012 #include <type_traits>
0013
0014 /**
0015  * @file TemplateTools.h
0016  * Useful template machinery. Based on Alexandrescu, "Modern C++ Design".
0017  */
0018
0019 namespace ThePEG {
0020
0021 /// Conversion between integers and types.
0022 template <int v>
0023 struct Int2Type
0024 {
0025   enum { value = v };
0026 };
0027
0028 /// Dummy type for ambiguous function signatures.
0029 struct DummyType {};
0030
0031 /** @endcond */
0032
0033 /// Selection mechanism for type-dependent implementations.
0034 enum ImplSelector { Dimensioned, Standard, Enumerated };
0035
0036 /// Typedef for dimensioned types.
0037 typedef Int2Type<Dimensioned> DimensionT;
0038
0039 /// Typedef for non-dimensioned types.
0040 typedef Int2Type<Standard> StandardT;
0041
0042 /// Typedef for non-dimensioned types.
0043 typedef Int2Type<Enumerated> EnumT;
0044
0045
0046 /// Type traits for built-in types
0047 template <typename T>
0048 struct TypeTraits
0049 {
0050   /// Boolean flag. Is true for physical quantities.
0051   enum { hasDimension = false };
0052   /// Implementation selector
0053   typedef StandardT DimType;
0054   /// Base unit for arithmetic types
0055   // construction with extra U type is necessary to make
0056   // enable_if work before concepts are supported properly
0057   template <typename U = T>
0058   static constexpr typename
0059   std::enable_if< (std::is_arithmetic<U>::value &&
0060                    std::is_same<U, T>::value), U>::type
0061   baseunit()
0062   { return static_cast<U>(1); }
0063 };
0064
0065 }
0066
0067 #endif