private AstNode Factor()
{
// FACTOR = UNARY-OP FACTOR |
// INCREMENT-BY-ONE VARIABLE |
// DECREMENT-BY-ONE VARIABLE |
// NUMBER (INCREMENT-BY-ONE) |
// NUMBER (DECREMENT-BY-ONE) |
// STRING | CHAR | BOOLEAN |
// PARAM-START EXPRESSION PARAM-END |
// VARIABLE
var token = _currentToken;
if (Tokens.IsUnaryOperator(token.Type))
{
Eat(token.Type); return(new UnaryOperationNode(token, Factor()));
}
else if (token.Type == Tokens.IncrementByOne)
{
Eat(token.Type); return(new PreIncrementNode(Variable()));
}
else if (token.Type == Tokens.DecrementByOne)
{
Eat(token.Type); return(new PreDecrementNode(Variable()));
}
else if (Tokens.IsNumberType(token.Type))
{
return(Number());
}
else if (token.Type == Tokens.String)
{
Eat(token.Type); return(new StringNode((string)token.Value));
}
else if (token.Type == Tokens.Character)
{
Eat(token.Type); return(new CharacterNode((char)token.Value));
}
else if (token.Type == Tokens.True)
{
Eat(token.Type); return(new BooleanNode(true));
}
else if (token.Type == Tokens.False)
{
Eat(token.Type); return(new BooleanNode(false));
}
else if (token.Type == Tokens.ParamStart)
{
Eat(Tokens.ParamStart);
var expression = Expression();
Eat(Tokens.ParamEnd);
return(expression);
}
else
{
var variable = Variable();
if (token.Type == Tokens.IncrementByOne)
{
Eat(token.Type); return(new PostIncrementNode(variable));
}
else if (token.Type == Tokens.DecrementByOne)
{
Eat(token.Type); return(new PostDecrementNode(variable));
}
return(variable);
}
throw new Exception("Factor bad. Very bad. No like it. Stop.");
}
