Tensor3_contracted.hpp

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/* A helper class that automatically returns the internal contraction
   of a rank 3 tensor. */
 
#pragma once
 
namespace FTensor
{
  /* Contracts second and third indices. */
 
  template <class A, class T, int Dim> class Tensor3_contracted_12
  {
    A iterA;
 
    template <int Current_Dim>
    T eval(const int N, const Number<Current_Dim> &) const
    {
      return iterA(N, Current_Dim - 1, Current_Dim - 1)
             + eval(N, Number<Current_Dim - 1>());
    }
    T eval(const int N, const Number<1> &) const { return iterA(N, 0, 0); }
 
  public:
    T operator()(const int N) const { return eval(N, Number<Dim>()); }
    Tensor3_contracted_12(const A &a) : iterA(a) {}
  };
 
  /* Contracts first and third indices. */
 
  template <class A, class T, int Dim> class Tensor3_contracted_02
  {
    A iterA;
 
    template <int Current_Dim>
    T eval(const int N, const Number<Current_Dim> &) const
    {
      return iterA(Current_Dim - 1, N, Current_Dim - 1)
             + eval(N, Number<Current_Dim - 1>());
    }
    T eval(const int N, const Number<1> &) const { return iterA(0, N, 0); }
 
  public:
    T operator()(const int N) const { return eval(N, Number<Dim>()); }
    Tensor3_contracted_02(const A &a) : iterA(a) {}
  };
 
  /* Contracts first and second indices. */
 
  template <class A, class T, int Dim> class Tensor3_contracted_01
  {
    A iterA;
 
    template <int Current_Dim>
    T eval(const int N, const Number<Current_Dim> &) const
    {
      return iterA(Current_Dim - 1, Current_Dim - 1, N)
             + eval(N, Number<Current_Dim - 1>());
    }
    T eval(const int N, const Number<1> &) const { return iterA(0, 0, N); }
 
  public:
    T operator()(const int N) const { return eval(N, Number<Dim>()); }
    Tensor3_contracted_01(const A &a) : iterA(a) {}
  };
}