One.hpp

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/**
 * @file One.hpp
 * @brief Constant Tensor1 expression with all components equal to one.
 */
 
#pragma once
 
namespace FTensor {
 
/**
 * @brief Stateless vector whose components are all equal to one.
 *
 * Contracting this expression with a Tensor1 sums its components:
 * @code
 * Index<'i', 3> i;
 * One<> t_one;
 * const auto sum = t_v(i) * t_one(i);
 * @endcode
 *
 * @tparam T Component type
 */
template <class T = int> class One {
public:
  constexpr T operator()(const int) const { return T(1); }
 
  template <char i, int Dim>
  Tensor1_Expr<One<T>, T, Dim, i>
  operator()(const Index<i, Dim> &) const {
    return Tensor1_Expr<One<T>, T, Dim, i>(*this);
  }
};
 
} // namespace FTensor