private void ReadIdentifierOrKeyword()
{
while (char.IsLetter(Current))
{
_position++;
}
var length = _position - _start;
var text = _text.ToString(_start, length);
_kind = SyntaxRules.GetKeywordKind(text);
}
public SyntaxToken Lex()
{
_start = _position;
_kind = SyntaxKind.BadToken;
_value = null;
// <operator> + - / ( )
switch (Current)
{
case '+':
{
_kind = SyntaxKind.PlusToken;
_position++;
break;
}
case '-':
{
_kind = SyntaxKind.MinusToken;
_position++;
break;
}
case '*':
{
_kind = SyntaxKind.StarToken;
_position++;
break;
}
case '/':
{
_kind = SyntaxKind.ForwardSlashToken;
_position++;
break;
}
case '(':
{
_kind = SyntaxKind.OpenParenToken;
_position++;
break;
}
case ')':
{
_kind = SyntaxKind.CloseParenToken;
_position++;
break;
}
case '{':
{
_kind = SyntaxKind.OpenBraceToken;
_position++;
break;
}
case '}':
{
_kind = SyntaxKind.CloseBraceToken;
_position++;
break;
}
case '&':
{
if (Lookahead == '&')
{
_kind = SyntaxKind.AmpersandAmpersandToken;
_position += 2;
}
break;
}
case '|':
{
if (Lookahead == '|')
{
_kind = SyntaxKind.PipePipeToken;
_position += 2;
}
break;
}
case '=':
{
_position++;
if (Current != '=')
{
_kind = SyntaxKind.EqualToken;
}
else
{
_kind = SyntaxKind.EqualEqualToken;
_position++;
}
break;
}
case '!':
{
_position++;
if (Current != '=')
{
_kind = SyntaxKind.BangToken;
}
else
{
_kind = SyntaxKind.BangEqualToken;
_position++;
}
break;
}
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
{
ReadNumberToken();
break;
}
case ' ':
case '\t':
case '\n':
case '\r':
{
ReadWhiteSpaceToken();
break;
}
case '\0':
{
_kind = SyntaxKind.EOFToken;
break;
}
default:
{
if (char.IsLetter(Current))
{
ReadIdentifierOrKeyword();
}
// <whitespace>
else if (char.IsWhiteSpace(Current))
{
ReadWhiteSpaceToken();
}
else
{
_diagnostics.ReportBadCharacter(_position, Current);
_position++;
}
break;
}
}
var length = _position - _start;
var text = SyntaxRules.GetText(_kind);
if (text == null)
{
text = _text.ToString(_start, length);
}
return(new SyntaxToken(_kind, _start, text, _value));
}
