// Print token
public static void PrintToken(string token, int tkCode)
{
Console.Write
("Lexeme: " + token.PadRight(10) + " Token Code: " + tkCode.ToString().PadRight(10));
Console.Write
(" Mnemonic: " + CodeTable.LookupCode(tkCode).PadRight(10));
// If token is within the symbol table, report it index
if (CodeTable.LookupName(CodeTable.LookupCode(tkCode)) == 50 ||
CodeTable.LookupName(CodeTable.LookupCode(tkCode)) == 51 ||
CodeTable.LookupName(CodeTable.LookupCode(tkCode)) == 52)
{
Console.Write
(" Symbol Table Index: " + symbolTable.LookupSymbol(token));
}
Console.WriteLine();
}
public static string GetNextToken(bool TraceOn)
{
Token newToken = new Token(); // Temporary Token storage
int currentState = 0; // The state of the DFA now
int previousState = 0; // The state of the DFA 1 step behind
bool continueBuilding = true; // Used to see if the token is over
string lexemeTobuild = ""; // The token string
// If we are out of characters, stop
if (fileToTokenize.EndOfStream)
{
EOF = true;
}
// If the token is over, or the file is completely read, stop
while (continueBuilding && !fileToTokenize.EndOfStream)
{
// Set to false if we need to not consume a character during
// this pass
if (readNextChar)
{
currentChar = Convert.ToChar(fileToTokenize.Read());
currentChar = char.ToUpper(currentChar);
}
if (IsNewline(currentChar))
{
currentLine += 1;
}
if (TraceOn && IsNewline(currentChar))
{
Console.WriteLine(currentLine - 1 + ": " + Trace.ReadLine());
}
// Save the state you are currently in in case the next state is exit
previousState = currentState;
// O P E R A T E T H E M A C H I N E
currentState = LEXDFA.storedDFA[GetCharacterDFAIndex(currentChar), currentState];
// Machine is not in an escape or error state
if (currentState != GET_OUT &&
currentState != COMMENT_NOT_ENDED &&
currentState != STRING_NOT_ENDED &&
currentState != UNREC_CHAR)
{
lexemeTobuild += currentChar;
readNextChar = true;
}
// Machine has just read a \n token out of context
// Escape this
else if ((currentState == GET_OUT && previousState == START))
{
continueBuilding = false;
readNextChar = true;
}
// Machine has just been put into the escape state
// Machine has constructed a valid token to this point (accept)
// Find out what kind of token it is and return it
else if (currentState == GET_OUT && LEXDFA.Includes(previousState))
{
continueBuilding = false;
readNextChar = false;
switch (previousState)
{
case 1: // Identifier found (variable)[string]
lexemeTobuild = TruncateIdentifier(lexemeTobuild);
// Don't add reserve words to symbol table
if (IsReserveWord(lexemeTobuild))
{
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = ReserveWordsTable.LookupName(lexemeTobuild);
}
// Do add other identifiers
else
{
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 50;
// Set global position in symbol table
positionInTable = AddToSymbolTable(newToken, 1);
}
break;
case 2: // Numeric Constant (constant)[integer]
lexemeTobuild = TruncateNumericConstant(lexemeTobuild);
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 51;
// Set global position in symbol table
positionInTable = AddToSymbolTable(newToken, 2);
break;
case 3: // Numeric Constant (constant)[float]
lexemeTobuild = TruncateNumericConstant(lexemeTobuild);
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 52;
// Set global position in symbol table
positionInTable = AddToSymbolTable(newToken, 3);
break;
case 6: // Numeric Constant (constant)[float+exp]
lexemeTobuild = TruncateNumericConstant(lexemeTobuild);
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 52;
// Set global position in symbol table
positionInTable = AddToSymbolTable(newToken, 3);
break;
case 9: // String found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 53;
positionInTable = AddToSymbolTable(newToken, 4);
break;
case 14: // (**) comment
// Ignore this one
newToken._lexeme = "";
newToken._tokenCode = 999;
nextToken = newToken._lexeme;
tokenCode = newToken._tokenCode;
break;
case 17: // ## comment
// Also here
newToken._lexeme = "";
newToken._tokenCode = 999;
nextToken = newToken._lexeme;
tokenCode = newToken._tokenCode;
break;
case 18: // / found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 30;
break;
case 19: // * found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 31;
break;
case 20: // + found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 32;
break;
case 21: // - found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 33;
break;
case 22: // ( found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 34;
break;
case 23: // ) found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 35;
break;
case 24: // ; found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 36;
break;
case 25: // : found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 47;
break;
case 26: // := found
newToken._lexeme = ":=";
newToken._tokenCode = 37;
break;
case 27: // > found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 38;
break;
case 28: // < found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 39;
break;
case 29: // >= found
newToken._lexeme = ">=";
newToken._tokenCode = 40;
break;
case 30: // <= found
newToken._lexeme = "<=";
newToken._tokenCode = 41;
break;
case 31: // = found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 42;
break;
case 32: // <> found
newToken._lexeme = "<>";
newToken._tokenCode = 43;
break;
case 33: // , found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 44;
break;
case 34: // [ found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 45;
break;
case 35: // ] found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 46;
break;
case 36: // . found
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 48;
break;
}
// Set the global string and get out
nextToken = newToken._lexeme;
tokenCode = newToken._tokenCode;
return(nextToken);
}
// Machine has just been put into the escape state
// Machine has constructed an invalid token (reject)
else if (currentState == GET_OUT && !LEXDFA.Includes(previousState))
{
continueBuilding = false;
if (previousState == COMMENT_BODY || previousState == COMMENT_ENDING_STAR)
{
Console.WriteLine
("//////////////////ERROR - Comment not closed before EOF - ERROR//////////////////");
}
}
// Machine has encountered a newline character before
// string fully terminates
else if (currentState == STRING_NOT_ENDED)
{
Console.WriteLine
("//////////////////ERROR - Unterminated String Found - ERROR//////////////////");
continueBuilding = false;
}
// Machine encountered non recognized character
else if (currentState == UNREC_CHAR)
{
lexemeTobuild += currentChar;
// Some undefined input character
newToken._lexeme = lexemeTobuild;
newToken._tokenCode = 99;
nextToken = newToken._lexeme;
tokenCode = newToken._tokenCode;
// Set token code to 99 and get out
continueBuilding = false;
readNextChar = true;
return(nextToken);
}
}
return(null);
}
