public static Node ParseFactor()
{
//Console.WriteLine("Parsing Factor");
//Factor rules
//1st -> num
//1st -> +
//1st -> -
//1st -> (
//+ -> factor
//- -> factor
//( -> expression
//expression -> )
//factor acts as num
Node root;
switch (tokens.actual.type)
{
case "INT":
root = new IntVal();
root.value = tokens.actual.value;
tokens.SelectNext();
return(root);
case "IDENTIFIER":
root = new Identifier((string)tokens.actual.value);
root.value = tokens.actual.value;
tokens.SelectNext();
return(root);
case "PLUS":
case "MINUS":
root = new UnOp();
root.value = tokens.actual.type == "PLUS" ? '+': '-';
tokens.SelectNext();
root.children[0] = ParseFactor();
return(root);
case "POPEN":
tokens.SelectNext();
root = ParseExpression();
if (tokens.actual.type != "PCLOSE")
{
throw new SystemException($"Missing closing parentesis (position {tokens.position}) [Line: {CurrentLine}]");
}
tokens.SelectNext();
return(root);
case "INPUT":
root = new UnOp();
root.value = "input";
tokens.SelectNext();
return(root);
}
//End of term reached, but exiting was not allowed
throw new SystemException($"Invalid expression format. Expression end was unexpected(position {tokens.position}) [Line: {CurrentLine}]");
}
public static Node ParseFactor()
{
//Console.WriteLine("Parsing Factor");
//Factor rules
//1st -> num
//1st -> +
//1st -> -
//1st -> not
//1st -> (
//+ -> factor
//- -> factor
//not -> factor
//( -> expression
//expression -> )
//identifier acts as num
//True | False acts as num
Node root;
switch (tokens.actual.type)
{
case "INT":
root = new IntVal();
root.value = tokens.actual.value;
tokens.SelectNext();
return(root);
case "IDENTIFIER":
root = new Identifier((string)tokens.actual.value);
root.value = tokens.actual.value;
tokens.SelectNext();
//check if this is a function
if (tokens.actual.type == "POPEN")
{
FuncCall call = new FuncCall();
call.value = root.value;
tokens.SelectNext();
if (tokens.actual.type != "PCLOSE")
{
do
{
if (tokens.actual.type == "COMMA")
{
tokens.SelectNext();
}
call.Add(ParseRelExpression());
} while(tokens.actual.type == "COMMA");
}
Expect("PCLOSE", true);
return(call);
}
return(root);
case "TRUE":
case "FALSE":
root = new UnOp();
root.value = tokens.actual.type == "TRUE" ? "true": "false";
tokens.SelectNext();
return(root);
case "PLUS":
case "MINUS":
root = new UnOp();
root.value = tokens.actual.type == "PLUS" ? '+': '-';
tokens.SelectNext();
root.children[0] = ParseFactor();
return(root);
case "NOT":
root = new UnOp();
root.value = "not";
tokens.SelectNext();
root.children[0] = ParseFactor();
return(root);
case "POPEN":
tokens.SelectNext();
root = ParseRelExpression();
if (tokens.actual.type != "PCLOSE")
{
throw new SystemException($"Missing closing parentesis (position {tokens.position}) [Line: {CurrentLine}]");
}
tokens.SelectNext();
return(root);
case "INPUT":
root = new UnOp();
root.value = "input";
tokens.SelectNext();
return(root);
}
//End of term reached, but exiting was not allowed
throw new SystemException($"Invalid expression format. Expression end was unexpected(position {tokens.position}) [Line: {CurrentLine}]");
}