Tensor1_times_Tensor1.hpp

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/* Multiplies two Tensor1's together yielding a T (int, double, etc.)
   or a Tensor2. */
 
/* A(i)*B(i) -> T */
 
#pragma once
 
namespace FTensor
{
  template <class A, class B, class T, class U, int Dim, char i,
            int Current_Dim>
  typename promote<T, U>::V
  T1_times_T1(const Tensor1_Expr<A, T, Dim, i> &a,
              const Tensor1_Expr<B, U, Dim, i> &b, const Number<Current_Dim> &)
  {
    return a(Current_Dim - 1) * b(Current_Dim - 1)
           + T1_times_T1(a, b, Number<Current_Dim - 1>());
  }
 
  template <class A, class B, class T, class U, int Dim, char i>
  typename promote<T, U>::V
  T1_times_T1(const Tensor1_Expr<A, T, Dim, i> &a,
              const Tensor1_Expr<B, U, Dim, i> &b, const Number<1> &)
  {
    return a(0) * b(0);
  }
 
  template <class A, class B, class T, class U, int Dim, char i>
  typename promote<T, U>::V operator*(const Tensor1_Expr<A, T, Dim, i> &a,
                                      const Tensor1_Expr<B, U, Dim, i> &b)
  {
    return T1_times_T1(a, b, Number<Dim>());
  }
 
  /* A(i)*B(j) -> Tensor2 */
 
  template <class A, class B, class T, class U, int Dim0, int Dim1, char i,
            char j>
  class Tensor1_times_Tensor1
  {
    Tensor1_Expr<A, T, Dim0, i> iterA;
    Tensor1_Expr<B, U, Dim1, j> iterB;
 
  public:
    Tensor1_times_Tensor1(const Tensor1_Expr<A, T, Dim0, i> &a,
                          const Tensor1_Expr<B, U, Dim1, j> &b)
        : iterA(a), iterB(b)
    {}
    typename promote<T, U>::V operator()(const int N1, const int N2) const
    {
      return iterA(N1) * iterB(N2);
    }
  };
 
  template <class A, class B, class T, class U, int Dim0, int Dim1, char i,
            char j>
  Tensor2_Expr<Tensor1_times_Tensor1<A, B, T, U, Dim0, Dim1, i, j>,
               typename promote<T, U>::V, Dim0, Dim1, i, j>
  operator*(const Tensor1_Expr<A, T, Dim0, i> &a,
            const Tensor1_Expr<B, U, Dim1, j> &b)
  {
    using TensorExpr = Tensor1_times_Tensor1<A, B, T, U, Dim0, Dim1, i, j>;
    return Tensor2_Expr<TensorExpr, typename promote<T, U>::V, Dim0, Dim1, i,
                        j>(TensorExpr(a, b));
  }
}