%{
import java.io.*;
import java.util.*;
/*  
All of the below productions that do not have associated 
actions are using the DEFAULT action -- $$ = $1 
*/

%}

%token PLUS TIMES CR RPAREN LPAREN EQUAL
%token <sval> ID
%token <ival> INT
%type <ival> term expr factor

%%
lines	:	lines line
	|	line
	;
line	:	expr CR 		{System.out.println("= " + $1+ "\n"); }
	|	ID EQUAL expr CR 	{ assign($1,$3); }
	;
expr	:	expr PLUS term 		{$$= $1+ $3; }
	|	term
	;
term	:	term TIMES factor	{$$= $1* $3; }
	|	factor
	;
factor	:	LPAREN expr RPAREN	{$$ = $2;}
	|	INT
	|	ID			{$$ = lookup($1); }
%%

/* Byacc/J expects a member method int yylex(). We need to provide one
   through this mechanism. See the jflex manual for more information. */

	/* reference to the lexer object */
	private scanner lexer;
	
	/* A simple symbol table */
	private HashMap symbol_table = new HashMap();

	/* interface to the lexer */
	private int yylex() {
		int retVal = -1;
		try {
			retVal = lexer.yylex();
		} catch (IOException e) {
			System.err.println("IO Error:" + e);
		}
		return retVal;
	}
	
	/* error reporting */
	public void yyerror (String error) {
		System.err.println("Error : " + error + " at line " + lexer.getLine());
	}

	/* constructor taking in File Input */
	public Parser (Reader r) {
		lexer = new scanner (r, this);
	}

	/* this method stores an id on the symbol table with its associated value */
	public void assign (String id, int value) {
		symbol_table.put (id, new Integer(value));
	}

	public int lookup (String id) {
		return ((Integer)symbol_table.get(id)).intValue();
	}
	public static void main (String [] args) throws IOException {
		Parser yyparser = new Parser(new FileReader(args[0]));
		yyparser.yyparse();
	}