/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

class CalcParser extends Parser;
options {
	buildAST = true;	// uses CommonAST by default
}

expr
	:	mexpr (PLUS^ mexpr)* SEMI!
	;

mexpr
	:	atom (STAR^ atom)*
	;

atom:	INT
	;

class CalcLexer extends Lexer;

WS	:	(' '
	|	'\t'
	|	'\n'
	|	'\r')
		{ _ttype = Token.SKIP; }
	;

LPAREN:	'('
	;

RPAREN:	')'
	;

STAR:	'*'
	;

PLUS:	'+'
	;

SEMI:	';'
	;

protected
DIGIT
	:	'0'..'9'
	;

INT	:	(DIGIT)+
	;

class CalcTreeWalker extends TreeParser;

expr returns [float r]
{
	float a,b;
	r=0;
}
	:	#(PLUS a=expr b=expr)	{r = a+b;}
	|	#(STAR a=expr b=expr)	{r = a*b;}
	|	i:INT			{r = (float)Integer.parseInt(i.getText());}
	;