public Token NextToken()
{
State = LexerState.Ready;
char c;
while (StringEnd != Input.Length)
{
c = read();
switchState(c);
if (State == LexerState.Accepted)
{
Token T = Accept(AcceptType);
if (T.Type != TokenType.Token_SKIP)
return T;
}
}
if (State == LexerState.Ready)
{
Token T = new Token();
T.Lexeme = "";
return T;
}
else
throw new LexerException("End of file reached");
}
public void Check()
{
for (int i = 0; i != TokensList.Count() - 1; i++)
{
CurrentToken = TokensList[i];
NextToken = TokensList[i + 1];
if (CurrentToken.Type == NextToken.Type)
{
if (CurrentToken.Lexeme != "{" && CurrentToken.Lexeme != "}" && CurrentToken.Lexeme != "(" && CurrentToken.Lexeme != ")")
Error = true;
break;
}
else if (CurrentToken.Type == TokenType.Token_INT_LITERAL && NextToken.Type == TokenType.Token_IDENTIFIER || CurrentToken.Type == TokenType.Token_INT_LITERAL && NextToken.Lexeme == "}" || CurrentToken.Type == TokenType.Token_INT_LITERAL && NextToken.Lexeme == "{")
{
Error = true;
break;
}
else if (CurrentToken.Type == TokenType.Token_INT_LITERAL && NextToken.Lexeme == "=")
{
Error = true;
break;
}
else if (CurrentToken.Lexeme != ";" && NextToken.Type == TokenType.Token_RESERVEDWORD)
{
if (CurrentToken.Lexeme != "{" && CurrentToken.Lexeme != "}"
&& CurrentToken.Lexeme != "(" && CurrentToken.Lexeme != ")")
{
Error = true;
break;
}
}
else if (CurrentToken.Lexeme != ";" && NextToken.Type == TokenType.Token_EOF)
{
if (CurrentToken.Lexeme == "}")
continue;
else
{
Error = true;
break;
}
}
}
if (Error)
{
throw new ParseException("Syntax Error.");
}
}
protected Token Accept(TokenType Type)
{
string Lexeme = Input.Substring(StringBegin, StringEnd - StringBegin);
StringBegin = StringEnd;
Token Temp = new Token();
Temp.Lexeme = Lexeme;
Temp.Type = Type;
State = LexerState.Ready;
if (Temp.Lexeme == "if" || Temp.Lexeme == "while" || Temp.Lexeme == "\r\nif" || Temp.Lexeme == "\r\nwhile")
Temp.Type = TokenType.Token_RESERVEDWORD;
TokensList.Add(Temp);
return Temp;
}
protected bool Match(TokenType TokenType)
{
if (Lookahead.Type == TokenType)
{
if (MoreTokens())
Lookahead = NextToken();
return true;
}
else
{
throw new ParseException("Expected " + " " + TokenType.ToString());
return false;
}
}
protected bool Match(string Lexeme)
{
if (Lookahead.Lexeme == Lexeme)
{
if (MoreTokens())
{
Lookahead = NextToken();
}
else
{
Lookahead = new Token();
Lookahead.Type =TokenType.Token_EOF;
}
return true;
}
else
{
throw new ParseException("Expected " + " " + Lexeme);
return false;
}
}
public void appendEOF()
{
Token temp = new Token(TokenType.Token_EOF, "");
TokensList.Add(temp);
}
public SyntaxChecker(List<Token> TokensList)
{
this.TokensList = TokensList;
CurrentToken = new Token();
NextToken = new Token();
}