ExecutionOutputLink.cc

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/*
 * opencog/atoms/execution/ExecutionOutputLink.cc
 *
 * Copyright (C) 2009, 2013, 2015 Linas Vepstas
 * All Rights Reserved
 *
 * 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 <stdlib.h>

#include <opencog/atomspace/atom_types.h>
#include <opencog/atomspace/AtomSpace.h>
#include <opencog/atoms/NumberNode.h>
#include <opencog/atoms/reduct/AssignLink.h>
#include <opencog/atoms/reduct/PlusLink.h>
#include <opencog/atoms/reduct/TimesLink.h>
#include <opencog/cython/PythonEval.h>
#include <opencog/guile/SchemeEval.h>

#include "ExecutionOutputLink.h"
#include "Instantiator.h"

using namespace opencog;

ExecutionOutputLink::ExecutionOutputLink(const HandleSeq& oset,
                                         TruthValuePtr tv,
                                         AttentionValuePtr av)
    : FunctionLink(EXECUTION_OUTPUT_LINK, oset, tv, av)
{
    if (2 != oset.size() or
       GROUNDED_SCHEMA_NODE != oset[0]->getType() or
       LIST_LINK != oset[1]->getType())
    {
        throw RuntimeException(TRACE_INFO,
            "ExecutionOutputLink must have schema and args!");
    }
}

ExecutionOutputLink::ExecutionOutputLink(const Handle& schema,
                                         const Handle& args,
                                         TruthValuePtr tv,
                                         AttentionValuePtr av)
    : FunctionLink(EXECUTION_OUTPUT_LINK, schema, args, tv, av)
{
    if (GROUNDED_SCHEMA_NODE != schema->getType())
        throw RuntimeException(TRACE_INFO, "Expecting GroundedSchemaNode!");

    if (LIST_LINK != args->getType())
        throw RuntimeException(TRACE_INFO,
            "ExecutionOutputLink must have schema and args!");
}

ExecutionOutputLink::ExecutionOutputLink(Link& l)
    : FunctionLink(l)
{
    Type tscope = l.getType();
    if (EXECUTION_OUTPUT_LINK != tscope)
        throw RuntimeException(TRACE_INFO,
            "Expection an ExecutionOutputLink!");
}

Handle ExecutionOutputLink::execute(AtomSpace* as) const
{
    return do_execute(as, _outgoing[0], _outgoing[1]);
}

Handle ExecutionOutputLink::do_execute(AtomSpace* as,
                         const Handle& gsn, const Handle& cargs)
{
    // Search for additional execution links, and execute them too.
    // We will know that happend if the returned handle differs from
    // the input handle. If the results are different, add the new
    // results to the atomspace. We need to do this, because scheme,
    // and python expects to find thier arguments in the atomspace,
    // but this is arguably broken, as it pollutes the atomspace with
    // junk that is never cleaned up.  We punt for now, but something
    // should be done about this. XXX FIXME ...
    Instantiator inst(as);
    LinkPtr largs(LinkCast(cargs));
    Handle args(cargs);
    if (largs)
    {
        std::vector<Handle> new_oset;
        bool changed = false;
        for (Handle ho : largs->getOutgoingSet())
        {
            Handle nh(inst.execute(ho));
            // nh might be NULL if ho was a DeleteLink
            if (nh != NULL)
                new_oset.push_back(nh);
            if (nh != ho) changed = true;
        }
        if (changed)
            args = as->add_link(LIST_LINK, new_oset);
    }

    // Get the schema name.
    const std::string& schema = NodeCast(gsn)->getName();
    // printf ("Grounded schema name: %s\n", schema.c_str());

    // At this point, we only run scheme and python schemas.
    if (0 == schema.compare(0,4,"scm:", 4))
    {
#ifdef HAVE_GUILE
        // Be friendly, and strip leading white-space, if any.
        size_t pos = 4;
        while (' ' == schema[pos]) pos++;

        SchemeEval* applier = SchemeEval::get_evaluator(as);
        Handle h(applier->apply(schema.substr(pos), args));

        // Exceptions were already caught, before leaving guile mode,
        // so we can't rethrow.  Just throw a new exception.
        if (applier->eval_error())
            throw RuntimeException(TRACE_INFO,
                "Failed evaluation; see logfile for stack trace.");
        return h;
#else
        throw RuntimeException(TRACE_INFO,
            "Cannot evaluate scheme GroundedSchemaNode!");
#endif /* HAVE_GUILE */
    }

    if (0 == schema.compare(0, 3,"py:", 3))
    {
#ifdef HAVE_CYTHON
        // Be friendly, and strip leading white-space, if any.
        size_t pos = 3;
        while (' ' == schema[pos]) pos++;

        // Get a reference to the python evaluator. 
        // Be sure to specify the atomspace in which the
        // evaluation is to be performed.
        PythonEval &applier = PythonEval::instance();
        Handle h = applier.apply(as, schema.substr(pos), args);

        // Return the handle
        return h;
#else
        throw RuntimeException(TRACE_INFO,
            "Cannot evaluate python GroundedSchemaNode!");
#endif /* HAVE_CYTHON */
    }

    // Unkown proceedure type.
    throw RuntimeException(TRACE_INFO,
        "Cannot evaluate unknown GroundedSchemaNode!");
}