//SumOp -> + Term SumOp
//SumOp -> - Term SumOp
//SumOp -> EPSILON
Factor SumOp(Factor t)
{
Factor t2;
switch (lookahead.type)
{
case TokenType.ADD:
GetNextToken();
t2 = Term();
t.Add(t2);
return(SumOp(t));
case TokenType.SUB:
GetNextToken();
t2 = Term();
t.Subtract(t2);
return(SumOp(t));
default:
return(t);
}
}
Factor Parse()
{
GetNextToken();
Factor t1 = Expression();
if (!eq.IsEquation && lookahead.type == TokenType.EOF)
{
return(t1);
}
if (!eq.IsEquation && lookahead.type != TokenType.EOF)
{
throw WrongSymbol("End of File", lookahead.text);
}
if (eq.IsEquation && lookahead.type != TokenType.EQUAL)
{
throw WrongSymbol("=", lookahead.text);
}
GetNextToken();
Factor t2 = Expression();
t1.Subtract(t2);
return(t1);
}
//SumOp -> + Term SumOp
//SumOp -> - Term SumOp
//SumOp -> EPSILON
Factor SumOp(Factor t)
{
Factor t2;
switch (lookahead.type) {
case TokenType.ADD:
GetNextToken ();
t2 = Term ();
t.Add (t2);
return SumOp (t);
case TokenType.SUB:
GetNextToken ();
t2 = Term ();
t.Subtract (t2);
return SumOp (t);
default:
return t;
}
}