UnifyPMCB.cc

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/*
 * UnifyPMCB.cc
 *
 * Copyright (C) 2015 OpenCog Foundation
 *
 * Author: William Ma <https://github.com/williampma>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License v3 as
 * published by the Free Software Foundation and including the exceptions
 * at http://opencog.org/wiki/Licenses
 *
 * 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 Affero General Public License
 * along with this program; if not, write to:
 * Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "UnifyPMCB.h"

using namespace opencog;

UnifyPMCB::UnifyPMCB(AtomSpace* as, VariableListPtr int_vars, VariableListPtr ext_vars)
    : BackwardChainerPMCB(as, int_vars), _ext_vars(ext_vars)
{

}

UnifyPMCB::~UnifyPMCB()
{

}

bool UnifyPMCB::variable_match(const Handle& npat_h,
                               const Handle& nsoln_h)
{
    Type soltype = nsoln_h->getType();

    // special case to allow any typed variable to match to a variable
    if (soltype == VARIABLE_NODE && _ext_vars->get_variables().varset.count(nsoln_h) == 1)
    {
        // if the variable is untyped, match immediately
        if (_ext_vars->get_variables().typemap.count(nsoln_h) == 0
            || _int_vars->get_variables().typemap.count(npat_h) == 0)
            return true;

        // otherwise the two variables type need to match
        if (_int_vars->get_variables().typemap.at(npat_h)
            == _ext_vars->get_variables().typemap.at(nsoln_h))
            return true;

        return false;
    }

    return BackwardChainerPMCB::variable_match(npat_h, nsoln_h);
}

bool UnifyPMCB::grounding(const std::map<Handle, Handle> &var_soln,
                          const std::map<Handle, Handle> &pred_soln)
{
    std::map<Handle, Handle> true_var_soln;

    // get rid of non-var mapping
    for (auto& p : var_soln)
    {
        if (_int_vars->get_variables().varset.count(p.first) == 1)
        {
            // check if any typed variable map to a variable, and if so,
            // store the reverse mapping
            if (DefaultPatternMatchCB::_type_restrictions->count(p.first) == 1
                && DefaultPatternMatchCB::_type_restrictions->at(p.first).count(p.second->getType()) == 0)
                true_var_soln[p.second] = p.first;
            else
                true_var_soln[p.first] = p.second;
        }
    }

    // store the variable solution
    var_solns_.push_back(true_var_soln);
    pred_solns_.push_back(pred_soln);

    return false;
}