map_some.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 __MAP_SOME_HH
# define __MAP_SOME_HH

# include "../strategies.hh"
# include "../generic/try.hh"
# include "map.hh"

namespace aurelia {

  template <typename S>
  struct map_some_strategy {
  private:
    S s;

  public:
    map_some_strategy(const S& s): s(s) {}
    map_some_strategy(const map_some_strategy& other): s(other.s) {}

    template <typename Pool>
    untyped_term<Pool> operator()(const untyped_term<Pool>& t) const {
      typedef typename strategy_concept<
        typename strategy_model<S, untyped_term<Pool> >::model>
        ::check require;

      typedef untyped_term<Pool> T;
      typedef untyped_constructor<Pool> C;

      if (t.constructor() == C::AS_LIST) {
        try {
          T a = s(t[0]);
          return T(C::AS_LIST, (a, map(try_(s))(t[1])));
        }
        catch (failure) {
          T b = (*this)(t[1]);
          return T(C::AS_LIST, (t[0], b));
        }
      }
      throw failure();
    }
  };

  template <typename S>
  map_some_strategy<S> map_some(const S& s) {
    return map_some_strategy<S>(s);
  }

}

#endif