private void CommonStartup()
{
keywords = new HashSet <string>
{
"if",
"while"
};
escapeLookup = new Dictionary <char, char>
{
{ 'n', '\n' },
{ 'r', '\r' },
{ 't', '\t' },
{ '\\', '\\' },
{ '"', '"' }
};
lineNumber = currentLineNumber = 1;
positionNumber = currentLexedPosition = 0; // cause we gonna call NextChar one time first.
isEOF = false;
currentValue = new StringBuilder(string.Empty);
StateFunction = RootState;
hasDecimalPlace = false;
// we begin by reading in the first character
NextChar();
}
private bool StringState(char c, out LexedToken token)
{
token = null;
if (c == '\\')
{
// we gonna get the escaped character from the next state
StateFunction = EscapeStringState;
// consume this slash
return(true);
}
else if (c == '"')
{
// return the built string
token = new LexedToken(LexedTokenType.String, currentValue.ToString());
// consume this closing quotes
return(true);
}
// build up the string
currentValue.Append(c);
return(true);
}
private bool EscapeStringState(char c, out LexedToken token)
{
token = null;
if (escapeLookup.ContainsKey(c))
{
// we support this escape character
currentValue.Append(escapeLookup[c]);
// set the state back to string builder
StateFunction = StringState;
// consume this character
return(true);
}
else
{
// return an invalid token and consume this
MarkPosition();
token = new LexedToken(LexedTokenType.Invalid, "\\" + c.ToString());
return(true);
}
}
/// <summary>
/// The initial state
/// </summary>
private bool RootState(char c, out LexedToken token)
{
token = null;
if (char.IsWhiteSpace(c)) // skip whitespaces
{
return(true);
}
if (char.IsLetter(c) || c == '_')
{
MarkPosition();
// we bumped into a letter
currentValue.Append(c);
// so we change to an appropriate state
StateFunction = LetterState;
// consume this character
return(true);
}
else if (char.IsDigit(c))
{
MarkPosition();
// we got a first digit, let's not consume it first and let the
// state function do that
StateFunction = NumberState;
return(false);
}
else if (c == '"')
{
MarkPosition();
// the start of a string
StateFunction = StringState;
// consume this character
return(true);
}
else if (c == '+')
{
token = SingularToken(LexedTokenType.OperatorPlus, c);
return(true);
}
else if (c == '-')
{
token = SingularToken(LexedTokenType.OperatorMinus, c);
return(true);
}
else if (c == '*')
{
token = SingularToken(LexedTokenType.OperatorMultiply, c);
return(true);
}
else if (c == '/')
{
token = SingularToken(LexedTokenType.OperatorDivide, c);
return(true);
}
else if (c == '(')
{
token = SingularToken(LexedTokenType.OpenParen, c);
return(true);
}
else if (c == ')')
{
token = SingularToken(LexedTokenType.CloseParen, c);
return(true);
}
else if (c == '{')
{
token = SingularToken(LexedTokenType.OpenBraces, c);
return(true);
}
else if (c == '}')
{
token = SingularToken(LexedTokenType.CloseBraces, c);
return(true);
}
else if (c == ';')
{
token = SingularToken(LexedTokenType.Semicolon, c);
return(true);
}
else if (c == '=')
{
MarkPosition();
// TODO: Transition to a state to get the ==
currentValue.Append(c);
token = new LexedToken(LexedTokenType.OperatorEqual, currentValue.ToString());
return(true);
}
MarkPosition();
currentValue.Append(c);
token = new LexedToken(LexedTokenType.Invalid, currentValue.ToString());
return(true);
}
private void ClearState()
{
currentValue.Clear();
StateFunction = RootState;
hasDecimalPlace = false;
}
