PARSER_BEGIN(ExpEval)

import java.io.*;

/** IPIPIPIPIPIPIP */
public class ExpEval {
  public static void main(String args[]) {
    System.out.println("Reading from " + args[0]);
    ExpEval parser;
    try
    {
		parser = new ExpEval(new FileInputStream(args[0]));
    }
    catch(FileNotFoundException e)
    {
		System.out.println("File not found : " + args[0]);
		return;
    }

    try
    {
		SimpleNode n = parser.Start();
		n.dump("");
		System.out.println("Done.");
    }
    catch (Exception e) {
		System.out.println("Error : ");
		System.out.println(e.getMessage());
		e.printStackTrace();
    }
  }
}

PARSER_END(ExpEval)

SKIP:
{
	" " | "\t" | "\r" | "\n"
}

TOKEN: /* NUMBER */
{
	<NUMBER: <NATURAL> <FLOATING> >
	| <#NATURAL: (["0"-"9"])+ >
	| <#FLOATING: ("." (["0"-"9"])+)? >
}

TOKEN: /* VARIABLE */
{
	<VARIABLE: <LETTER> (<LETTER>|<DIGIT>)*>
	| <#LETTER: ["a"-"z", "A"-"Z"] >
	| <#DIGIT: ["0"-"9"] >
}

TOKEN: /* OPERATOR */
{
	<PLUS: "+">
	| <MINUS: "-">
	| <TIMES: "*">
	| <DIVIDE: "/">
	| <MODULO: "%">
}

void Natural() : {Token t;}
{
	t=<NUMBER> { jjtThis.val = t.image; }
}

void Number() : {}
{
	(Minus())? Natural()
}

void Variable() : {Token t;}
{
	t=<VARIABLE> { jjtThis.val = t.image; }
}

void Plus() : {Token t;}
{
	t=<PLUS> {jjtThis.op = "+";}
}

void Minus() : {Token t;}
{
	t=<MINUS> {jjtThis.op = "-";}
}

void Times() : {Token t;}
{
	t=<TIMES> {jjtThis.op = "*";}
}

void Divide() : {Token t;}
{
	t=<DIVIDE> {jjtThis.op = "/";}
}

void Modulo() : {Token t;}
{
	t=<MODULO> {jjtThis.op = "%";}
}

void PlusOp(): {}
{
	Plus() product()
}

void MinusOp(): {}
{
	Minus() product()
}

SimpleNode Start(): {}
{
	sum() <EOF>
	{ return jjtThis; }
}

/* Somme = Produit, {(+|-), Produit} */
void sum():
{}
{
	product() products()
}

void products():
{}
{
	(PlusOp() | MinusOp())*
}

void TimesOp(): {}
{
	Times() term()
}

void DivideOp(): {}
{
	Divide() term()
}

void ModuloOp(): {}
{
	Modulo() term()
}

/* Produit = Terme, {(+|/|%), Terme} */
void product():
{}
{
	term() terms()
}

void terms():
{}
{
	(TimesOp() | DivideOp() | ModuloOp())*
}

/* Terme = "(",Somme,")" | Nombre | Variable */
void term():
{}
{
	"(" sum() ")" | Number() | Variable()
}