identity.hh

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                             */
/*   This file is part of the C++-library RFFGen.                              */
/*   Copyright 2015 Lars Lubkoll                                               */
/*                                                                             */
/*   RFFGen is free software: you can redistribute it and/or modify            */
/*   it under the terms of the GNU General Public License as published by      */
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/*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             */
/*   GNU General Public License for more details.                              */
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef RFFGEN_IDENTITY_HH
#define RFFGEN_IDENTITY_HH

#include "Util/base.hh"
#include "Util/chainer.hh"

namespace RFFGen
{
  template <class> struct ArithmeticConceptCheck;
  template <class Arg, class = ArithmeticConceptCheck<Arg> >
  struct Identity : Base , Chainer< Identity<Arg,ArithmeticConceptCheck<Arg> > >
  {
    Identity() = default;

    Identity(const Arg& x) { update(x); }

    void update(const Arg& x)
    {
      x_ = x;
    }

    const Arg& d0() const noexcept { return x_; }

    template <int>
    const Arg& d1(const Arg& dx) const noexcept { return dx; }

  private:
    Arg x_;
  };

  template <class Arg>
  auto identity(const Arg& x)
  {
    return Identity<Arg>(x);
  }
}

#endif // RFFGEN_IDENTITY_HH