Promise.h

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/*CXXR $Id: Promise.h 1353 2013-03-18 16:59:38Z arr $
 *CXXR
 *CXXR This file is part of CXXR, a project to refactor the R interpreter
 *CXXR into C++.  It may consist in whole or in part of program code and
 *CXXR documentation taken from the R project itself, incorporated into
 *CXXR CXXR (and possibly MODIFIED) under the terms of the GNU General Public
 *CXXR Licence.
 *CXXR 
 *CXXR CXXR is Copyright (C) 2008-13 Andrew R. Runnalls, subject to such other
 *CXXR copyrights and copyright restrictions as may be stated below.
 *CXXR 
 *CXXR CXXR is not part of the R project, and bugs and other issues should
 *CXXR not be reported via r-bugs or other R project channels; instead refer
 *CXXR to the CXXR website.
 *CXXR */

/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1999-2006   The R Development Core Team.
 *
 *  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 2.1 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, a copy is available at
 *  http://www.r-project.org/Licenses/
 */

#ifndef RPROMISE_H
#define RPROMISE_H

#include "CXXR/RObject.h"
// Just to pick up define of BYTECODE:
#include "CXXR/Evaluator.h"

#ifdef __cplusplus

#include <boost/serialization/access.hpp>
#include <boost/serialization/base_object.hpp>
#include <boost/serialization/nvp.hpp>

#include "CXXR/Expression.h"
#include "CXXR/Environment.h"
#include "CXXR/Symbol.h"

namespace CXXR {
    class Promise : public RObject {
    public:
        Promise(RObject* valgen, Environment* env)
            : RObject(PROMSXP), m_value(env ? Symbol::unboundValue() : valgen),
              m_valgen(valgen), m_environment(env), m_under_evaluation(false),
              m_interrupted(false)
        {}

        Environment* environment() const
        {
            return m_environment;
        }

        RObject* force()
        {
            return evaluate(0);
        }

        bool isMissingSymbol() const;

        void setValue(RObject* val);

        static const char* staticTypeName()
        {
            return "promise";
        }

        RObject* value()
        {
            return m_value;
        }

        const RObject* valueGenerator() const
        {
            return m_valgen;
        }

        RObject* evaluate(Environment* env);
        const char* typeName() const;

        // Virtual function of GCNode:
        void visitReferents(const_visitor* v) const;
    protected:
        // Virtual function of GCNode:
        void detachReferents();
    private:
        friend class boost::serialization::access;

        GCEdge<> m_value;
        GCEdge<RObject> m_valgen;
        GCEdge<Environment> m_environment;
        mutable bool m_under_evaluation;
        mutable bool m_interrupted;

        // Declared private to ensure that Environment objects are
        // created only using 'new':
        ~Promise() {}

        // Not (yet) implemented.  Declared to prevent
        // compiler-generated versions:
        Promise(const Promise&);
        Promise& operator=(const Promise&);

        // Fields not serialised here are set up by the constructor:
        template <class Archive>
        void serialize(Archive& ar, const unsigned int version)
        {
            ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(RObject);
            GCNPTR_SERIALIZE(ar, m_value);
        }
    };

    inline RObject* forceIfPromise(RObject* object)
    {
        if (object && object->sexptype() == PROMSXP)
            object = static_cast<Promise*>(object)->force();
        return object;
    }
}  // namespace CXXR

BOOST_CLASS_EXPORT_KEY(CXXR::Promise)

namespace boost {
    namespace serialization {
        template<class Archive>
        void load_construct_data(Archive& ar, CXXR::Promise* t,
                                 const unsigned int version)
        {
            using namespace CXXR;
            GCStackRoot<> valgen;
            GCNPTR_SERIALIZE(ar, valgen);
            GCStackRoot<Environment> env;
            GCNPTR_SERIALIZE(ar, env);
            new (t) Promise(valgen, env);
        }

        template<class Archive>
        void save_construct_data(Archive& ar, const CXXR::Promise* t,
                                 const unsigned int version)
        {
            using namespace CXXR;
            const RObject* valgen = t->valueGenerator();
            GCNPTR_SERIALIZE(ar, valgen);
            const Environment* env = t->environment();
            GCNPTR_SERIALIZE(ar, env);
        }
    }  // namespace serialization
}  // namespace boost

extern "C" {
#endif

    SEXP Rf_mkPROMISE(SEXP expr, SEXP env);

#ifndef __cplusplus
    SEXP PRCODE(SEXP x);
#else
    inline SEXP PRCODE(SEXP x)
    {
        using namespace CXXR;
        const Promise& prom = *SEXP_downcast<Promise*>(x);
        return const_cast<RObject*>(prom.valueGenerator());
    }
#endif

#ifndef __cplusplus
    SEXP PRENV(SEXP x);
#else
    inline SEXP PRENV(SEXP x)
    {
        using namespace CXXR;
        const Promise& prom = *SEXP_downcast<Promise*>(x);
        return prom.environment();
    }
#endif

#ifndef __cplusplus
    SEXP PRVALUE(SEXP x);
#else
    inline SEXP PRVALUE(SEXP x)
    {
        using namespace CXXR;
        Promise& prom = *SEXP_downcast<Promise*>(x);
        return prom.value();
    }
#endif

    void SET_PRVALUE(SEXP x, SEXP v);

    // PREXPR() behaves similarly to valueGenerator(), but has special
    // (but apparently undocumented) behaviour if m_valgen (PRCODE) is
    // bytecode.  My guess is that if the bytecode evaluates to a
    // symbol, PREXPR returns that symbol, otherwise R_NilValue.
#ifdef BYTECODE
    SEXP R_PromiseExpr(SEXP);
#define PREXPR(e) R_PromiseExpr(e)
#else
#define PREXPR(e) PRCODE(e)
#endif

#ifdef __cplusplus
}
#endif

#endif /* RPROMISE_H */