public class Equation {

	private boolean debug;

	private String nextToken;	
	private TokenIter itTokens;
	
	Tree exprTree;
    
	public Equation(TokenIter iter, boolean debug){
		itTokens = iter;
		this.debug = debug;
                // put the first token from iter in nextToken
                // initial indent ""
		nextTok("");
	}

	private void error(String errMess) throws ParseException{
		throw new ParseException(errMess);

	}

	// line parses a line: lhs "=" expr
	// lhs is an identifier
	// and stores an IdVal (lhs, value) in the symbol table
	public Symbol line(BST symbolTable) throws BSTException, ParseException{
		TreeNode root;
		exprTree = null;
		if(nextToken==null)
			return null;
		else {
			if(debug)
				System.out.println("line");

			// scan left hand side String lhs
			// if it is not an identifier
			// call	error("Identifier expected");
			// if no next token
			// call	error("unexpected end of line");
			// scan "="
			// if not "=" call error("= expected");
			// parse expression and create expression tree
                        // evaluate Expression tree
                        // create Symbol lhsVal (lhs, value)
                        // insert lhsVal in symbolTable
			// if(debug)
			//	System.out.println("retrieving " + lhs + ": " + symbolTable.retrieveItem(lhs));
			// if(nextToken!=null){
			//	error("end of line expected");
			//	return null; 
			//} else 
			return lhsVal;

		}
	}
}