/** @file relational.cpp
 *
 *  Implementation of relations between expressions */

/*
 *  GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
 *
 *  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 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, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdexcept>

#include "relational.h"
#include "numeric.h"
#include "print.h"
#include "archive.h"
#include "utils.h"
#include "debugmsg.h"

namespace GiNaC {

GINAC_IMPLEMENT_REGISTERED_CLASS(relational, basic)

//////////
// default ctor, dtor, copy ctor assignment operator and helpers
//////////

relational::relational() : basic(TINFO_relational)
{
	debugmsg("relational default ctor",LOGLEVEL_CONSTRUCT);
}

void relational::copy(const relational & other)
{
	basic::copy(other);
	lh=other.lh;
	rh=other.rh;
	o=other.o;
}

DEFAULT_DESTROY(relational)

//////////
// other ctors
//////////

// public

relational::relational(const ex & lhs, const ex & rhs, operators oper) : basic(TINFO_relational)
{
	debugmsg("relational ctor ex,ex,operator",LOGLEVEL_CONSTRUCT);
	lh=lhs;
	rh=rhs;
	o=oper;
}

//////////
// archiving
//////////

relational::relational(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst)
{
	debugmsg("relational ctor from archive_node", LOGLEVEL_CONSTRUCT);
	unsigned int opi;
	if (!(n.find_unsigned("op", opi)))
		throw (std::runtime_error("unknown relational operator in archive"));
	o = (operators)opi;
	n.find_ex("lh", lh, sym_lst);
	n.find_ex("rh", rh, sym_lst);
}

void relational::archive(archive_node &n) const
{
	inherited::archive(n);
	n.add_ex("lh", lh);
	n.add_ex("rh", rh);
	n.add_unsigned("op", o);
}

DEFAULT_UNARCHIVE(relational)

//////////
// functions overriding virtual functions from bases classes
//////////

// public

void relational::print(const print_context & c, unsigned level) const
{
	debugmsg("relational print",LOGLEVEL_PRINT);

	if (is_of_type(c, print_tree)) {

		inherited::print(c, level);

	} else {

		if (precedence() <= level)
			c.s << "(";
		lh.print(c, precedence());
		switch (o) {
		case equal:
			c.s << "==";
			break;
		case not_equal:
			c.s << "!=";
			break;
		case less:
			c.s << "<";
			break;
		case less_or_equal:
			c.s << "<=";
			break;
		case greater:
			c.s << ">";
			break;
		case greater_or_equal:
			c.s << ">=";
			break;
		default:
			c.s << "(INVALID RELATIONAL OPERATOR)";
		}
		rh.print(c, precedence());
		if (precedence() <= level)
			c.s << ")";
	}
}

bool relational::info(unsigned inf) const
{
	switch (inf) {
	case info_flags::relation:
		return 1;
	case info_flags::relation_equal:
		return o==equal;
	case info_flags::relation_not_equal:
		return o==not_equal;
	case info_flags::relation_less:
		return o==less;
	case info_flags::relation_less_or_equal:
		return o==less_or_equal;
	case info_flags::relation_greater:
		return o==greater;
	case info_flags::relation_greater_or_equal:
		return o==greater_or_equal;
	}
	return 0;
}

unsigned relational::nops() const
{
	return 2;
}

ex & relational::let_op(int i)
{
	GINAC_ASSERT(i>=0);
	GINAC_ASSERT(i<2);

	return i==0 ? lh : rh;
}

ex relational::eval(int level) const
{
	if (level==1)
		return this->hold();
	
	if (level == -max_recursion_level)
		throw(std::runtime_error("max recursion level reached"));
	
	return (new relational(lh.eval(level-1),rh.eval(level-1),o))->setflag(status_flags::dynallocated | status_flags::evaluated);
}

ex relational::simplify_ncmul(const exvector & v) const
{
	return lh.simplify_ncmul(v);
}

// protected

int relational::compare_same_type(const basic & other) const
{
	GINAC_ASSERT(is_exactly_of_type(other, relational));
	const relational &oth = static_cast<const relational &>(other);
	
	if (o == oth.o) {
		int cmpval = lh.compare(oth.lh);
		if (cmpval)
			return cmpval;
		else
			return rh.compare(oth.rh);
	}
	return (o < oth.o) ? -1 : 1;
}

unsigned relational::return_type(void) const
{
	GINAC_ASSERT(lh.return_type()==rh.return_type());
	return lh.return_type();
}
   
unsigned relational::return_type_tinfo(void) const
{
	GINAC_ASSERT(lh.return_type_tinfo()==rh.return_type_tinfo());
	return lh.return_type_tinfo();
}

//////////
// new virtual functions which can be overridden by derived classes
//////////

/** Left hand side of relational. */
ex relational::lhs(void) const
{
	return lh;
}

/** Right hand side of relational. */
ex relational::rhs(void) const
{
	return rh;    
}

//////////
// non-virtual functions in this class
//////////

/** Cast the relational into a boolean, mainly for evaluation within an 
 *  if-statement.  Note that (a<b) == false does not imply (a>=b) == true in
 *  the general symbolic case.  A false result means the comparison is either
 *  false or undecidable (except of course for !=, where true means either
 *  unequal or undecidable). */
relational::operator bool() const
{
	const ex df = lh-rh;
	if (!is_ex_exactly_of_type(df,numeric))
		// cannot decide on non-numerical results
		return o==not_equal ? true : false;
	
	switch (o) {
	case equal:
		return ex_to<numeric>(df).is_zero();
	case not_equal:
		return !ex_to<numeric>(df).is_zero();
	case less:
		return ex_to<numeric>(df)<_num0();
	case less_or_equal:
		return ex_to<numeric>(df)<=_num0();
	case greater:
		return ex_to<numeric>(df)>_num0();
	case greater_or_equal:
		return ex_to<numeric>(df)>=_num0();
	default:
		throw(std::logic_error("invalid relational operator"));
	}
}

} // namespace GiNaC