public static Node ParseProgram()
{
//Diagram rules
//1st -> SubDec | FuncDec
//SubDec | FuncDec -> SubDec | FuncDec
//SubDec | FuncDec -> EOF
Statements root = new Statements();
while (tokens.actual.type != "EOF")
{
if (tokens.actual.type == "SUB" || tokens.actual.type == "FUNCTION")
{
root.Add(ParseFunction());
}
else
{
if (tokens.actual.type == "LINEBREAK")
{
CurrentLine++;
tokens.SelectNext();
}
else
{
throw new SystemException($"Statement line outside functions are not allowed. Got a {tokens.actual.type}.(position {tokens.position}) [Line: {CurrentLine}]");
}
}
}
//add a main funccall
FuncCall mainCall = new FuncCall();
mainCall.value = "main";
root.Add(mainCall);
return(root);
}
public static Node ParseFactor()
{
//Console.WriteLine("Parsing Factor");
//Factor rules
//1st -> num
//1st -> +
//1st -> -
//1st -> not
//1st -> (
//+ -> factor
//- -> factor
//not -> factor
//( -> expression
//expression -> )
//identifier acts as num
//True | False acts as num
Node root;
switch (tokens.actual.type)
{
case "INT":
root = new IntVal();
root.value = tokens.actual.value;
tokens.SelectNext();
return(root);
case "IDENTIFIER":
root = new Identifier((string)tokens.actual.value);
root.value = tokens.actual.value;
tokens.SelectNext();
//check if this is a function
if (tokens.actual.type == "POPEN")
{
FuncCall call = new FuncCall();
call.value = root.value;
tokens.SelectNext();
if (tokens.actual.type != "PCLOSE")
{
do
{
if (tokens.actual.type == "COMMA")
{
tokens.SelectNext();
}
call.Add(ParseRelExpression());
} while(tokens.actual.type == "COMMA");
}
Expect("PCLOSE", true);
return(call);
}
return(root);
case "TRUE":
case "FALSE":
root = new UnOp();
root.value = tokens.actual.type == "TRUE" ? "true": "false";
tokens.SelectNext();
return(root);
case "PLUS":
case "MINUS":
root = new UnOp();
root.value = tokens.actual.type == "PLUS" ? '+': '-';
tokens.SelectNext();
root.children[0] = ParseFactor();
return(root);
case "NOT":
root = new UnOp();
root.value = "not";
tokens.SelectNext();
root.children[0] = ParseFactor();
return(root);
case "POPEN":
tokens.SelectNext();
root = ParseRelExpression();
if (tokens.actual.type != "PCLOSE")
{
throw new SystemException($"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($"Invalid expression format. Expression end was unexpected(position {tokens.position}) [Line: {CurrentLine}]");
}
//public static Node ParseStatements(string poi){
// return ParseStatements("none");
// }
public static Node ParseStatement()
{
//Console.WriteLine("parsing expression");
//Diagram rules
//1st - Identfier
//identifier - =
//= - expression
//1st - print
//print - expression
//1st - statements
Node root;
//TODO- condense this code by replacing similar code with some functions (expect line end for example)
switch (tokens.actual.type)
{
case "END":
return(new NoOp());
case "IDENTIFIER":
// IDENTIFIER - = - EXPRESSION
// get identifier
Identifier ident = new Identifier((string)tokens.actual.value);
tokens.SelectNext();
if (tokens.actual.type != "EQUAL") //expecting a EQUAL
{
throw new SystemException($"Identifier with no assignment ({tokens.actual.value}) (position {tokens.position}) [Line: {CurrentLine}]");
}
root = new BinOp(); //create the assign biop node
root.value = '=';
root.children[0] = ident; //left is the identfier
tokens.SelectNext();
root.children[1] = ParseRelExpression(); //right is a relative expression
if (tokens.actual.type != "LINEBREAK") //expect linebreak after the expression;
{
throw new SystemException($"No LINEBREAK after assignment (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
return(root);
case "CALL":
tokens.SelectNext();
Expect("IDENTIFIER", false);
FuncCall call = new FuncCall();
call.value = (string)tokens.actual.value;
tokens.SelectNext();
Expect("POPEN", true);
if (tokens.actual.type != "PCLOSE")
{
do
{
if (tokens.actual.type == "COMMA")
{
tokens.SelectNext();
}
call.Add(ParseRelExpression());
}while (tokens.actual.type == "COMMA");
}
Expect("PCLOSE", true);
return(call);
case "PRINT":
//print - expression
root = new UnOp();
root.value = "print";
tokens.SelectNext();
root.children[0] = ParseRelExpression();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after the expression;
{
throw new SystemException($"No LINEBREAK after PRINT (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
return(root);
case "WHILE":
root = new WhileNode();
tokens.SelectNext();
root.children[0] = ParseRelExpression();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after the expression;
{
throw new SystemException($"No LINEBREAK after Relative Expression (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
root.children[1] = ParseStatements("while"); //already goes to next line, no select next required
return(root);
case "DIM":
root = new BinOp();
root.value = "vardec";
tokens.SelectNext();
if (tokens.actual.type != "IDENTIFIER")
{
throw new SystemException($"IDENTIFIER is required after an variable declaration declaration (position {tokens.position}) [Line: {CurrentLine}]");
}
root.children[0] = new NoOp();
root.children[0].value = (string)tokens.actual.value;
tokens.SelectNext();
if (tokens.actual.type != "AS")
{
throw new SystemException($"'As' is required in an variable declaration (position {tokens.position}) [Line: {CurrentLine}]");
}
tokens.SelectNext();
root.children[1] = parseType();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after the expression;
{
throw new SystemException($"No LINEBREAK after Variable declaration(position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
return(root);
case "IF":
root = new IfNode();
tokens.SelectNext();
root.children[0] = ParseRelExpression();
if (tokens.actual.type != "THEN") //expect THEN after the rel expression;
{
throw new SystemException($"THEN is required after an IF's Relative Expression (position {tokens.position}) [Line: {CurrentLine}]");
}
tokens.SelectNext();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after THEN;
{
throw new SystemException($"No LINEBREAK after Relative Expression (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
root.children[1] = ParseStatements("if"); //already goes to next line, no select next required
if (tokens.actual.type == "ELSE")
{
tokens.SelectNext();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after ELSE;
{
throw new SystemException($"No LINEBREAK after ELSE (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
root.children[2] = ParseStatements("else"); //left the token after the END, so it is probably on IF (END IF\n)
}
if (tokens.actual.type != "IF") //expect IF after the statements END for END IF\n construction;
{
throw new SystemException($"IF section end symbol not found, found END instead of END IF (position {tokens.position}) [Line: {CurrentLine}]");
}
tokens.SelectNext();
if (tokens.actual.type != "LINEBREAK") //expect linebreak after THEN;
{
throw new SystemException($"No LINEBREAK after Relative Expression (position {tokens.position}) [Line: {CurrentLine}]");
}
CurrentLine++;
tokens.SelectNext(); //go to next token after linebreak
return(root);
default:
return(new NoOp());
}
}
