SelectionVariable.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
 
#pragma once
 
 
// is expanded as the string value for X
#define STRING_NAME(X) #X
// is expanded as the function "static const std::string name(void)" which returns the string value of Y
#define PUT_NAME_FUNCTION(Y) static const std::string name(void) {return STRING_NAME(Y); };
 
#include <string>
#include <functional>
 
namespace Belle2 {
  template <class templateArgumentType, size_t Nargs, class templateReturnType = double>
  class SelectionVariable {
 
    template <size_t n, class returnType, class parameterType, class ... Ts>
    struct FunctionOf {
      typedef typename FunctionOf < n - 1, returnType, parameterType,
              parameterType, Ts... >::functionType functionType;
    };
 
    template <class returnType, class parameterType, class ... Ts>
    struct FunctionOf<0, returnType, parameterType, Ts...> {
      typedef std::function<returnType(Ts...)> functionType;
    };
 
  public:
 
    typedef templateReturnType variableType;
 
    typedef templateArgumentType argumentType;
 
    typedef typename FunctionOf<Nargs, variableType,
            const argumentType&>::functionType functionType;
 
    static const size_t c_Nargs = Nargs;
 
    inline static variableType
    value(const templateArgumentType& arg1, const templateArgumentType& arg2);
 
    virtual ~SelectionVariable() {};
 
    SelectionVariable() {};
 
  };
 
#define SELECTION_VARIABLE( variableName, nArgs, argumentType, implementation ) \
  class variableName:             \
    public SelectionVariable< argumentType , nArgs, double >     \
  {                 \
  public:               \
    static const std::string name(void) {return #variableName; };   \
    implementation              \
  };                  \
 
}