constant.hh

// This file is a part of Aurelia.
// Copyright (C) 2010  Valentin David
// Copyright (C) 2010  University of Bergen
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
#ifndef __CONSTANT_HH
# define __CONSTANT_HH

# include "pattern.hh"
//# include "../lists/listable.hh"

namespace aurelia {

  template <typename T>
  struct constant {
  private:
    T value;

  public:
    constant() = delete;
    constant(const constant& v): value(v.value) {
    }

    constant(constant&& v): value(std::move(v.value)) {
    }

    constant(const T& v): value(v) {
    }

    constant(T&& v): value(std::move(v)) {
    }

    template <typename U,
              typename = typename
              std::enable_if<std::is_convertible<U, T>::value>::type>
    constant(const U& v): value(v) {}

    template <typename U,
              typename = typename
              std::enable_if<std::is_convertible<U, T>::value>::type>
    constant(U&& v): value(std::move(v)) {}

    const T& operator*() const {
      return value;
    }

    const T& operator=(const T& c) const {
      if (value != c)
        throw failure();
      return value;
    }

  };

  template <typename T>
  struct pattern_model<constant<T> > {
    struct model {
      typedef constant<T> type;
      typedef T build_type;
    };
  };

  template <typename T>
  struct listable_model<constant<T> > {
    struct model {
      typedef constant<T> type;
    };
  };

}

#endif