DocScript SVN

/*
 * A simple expression to LaTeX translator: the parser

 * Copyright (C) 2009
 * Andreas Harnack (ah8 at freenet dot de)

 * This software 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 library; see the file COPYING.  If not, write to the Free
 * Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
 * USA.

 * As a special exception, you may use this file as part of a free software
 * library without restriction.  Specifically, if other files instantiate
 * templates or use macros or inline functions from this file, or you compile
 * this file and link it with other files to produce an executable, this
 * file does not by itself cause the resulting executable to be covered by
 * the GNU General Public License.  This exception does not however
 * invalidate any other reasons why the executable file might be covered by
 * the GNU General Public License.
 */

#include "parser.h"

fp expression(Input& input)
{
	fp expr = term(input);
	while ( 1 )
		if ( input() == '+' )
			expr = fp(new BinaryOp(expr, "+" , term(input.next())));
		else if ( input() == '-' )
			expr = fp(new BinaryOp(expr, "-" , term(input.next())));
		else
			break;
	return expr;
}

fp term(Input& input)
{
	fp expr = factor(input);
	while ( 1 )
		if ( input() == '*' )
			expr = fp(new BinaryOp(expr, "\\times" , factor(input.next())));
		else if ( input() == '/' )
			expr = fp(new BinaryOp(expr, "\\divides" , factor(input.next())));
		else
			break;
	return expr;
}

fp factor(Input& input)
{
	fp expr;
	if ( input() == Input::Number )
		expr = fp(new Number(input.number())), input.next();
	else if ( input() == '-' )
		expr = fp(new UnaryOp("-", expression(input.next())));
	else if ( input() == '(' ) {
		expr = fp(new Parentheses(expression(input.next())));
		if ( input() == ')' )
			input.next();
		else
			throw "')' expected";
	}
	else
		throw "factor expected";
	return expr;
}