private void ReadIdentifierOrKeyword()
{
while (char.IsLetter(Current))
{
Next();
}
var length = _position - _start;
var text = _text.ToString(_start, length);
_kind = SyntaxFacts.GetKeywordKind(text);
switch (_kind)
{
case SyntaxKind.LetKeyword:
case SyntaxKind.VarKeyword:
case SyntaxKind.IfKeyword:
case SyntaxKind.ElseKeyword:
case SyntaxKind.Identifier:
case SyntaxKind.WhileKeyword:
case SyntaxKind.ForKeyword:
case SyntaxKind.ToKeyword:
_value = text;
break;
case SyntaxKind.TrueKeyword:
_value = true;
break;
case SyntaxKind.FalseKeyword:
_value = false;
break;
default:
throw new Exception("Unknown identifier");
}
}
private void ReadIdentifierOrKeyword()
{
while (char.IsLetter(Current))
{
_position++;
}
var length = _position - _start;
var text = _text.ToString(_start, length);
_kind = SyntaxFacts.GetKeywordKind(text);
}
private void ReadIdentifierOrKeyword()
{
while (char.IsLetter(Current))
{
position++;
}
var length = position - start;
var t = text.ToString(start, length);
kind = SyntaxFacts.GetKeywordKind(t);
}
public SyntaxToken Lex()
{
if (_position >= _text.Length)
{
return(new SyntaxToken(SyntaxKind.EndOfFileToken, _position, "\0", null));
}
if (char.IsDigit(Current))
{
var start = _position;
while (char.IsDigit(Current))
{
Next();
}
var length = _position - start;
var text = _text.Substring(start, length);
if (!int.TryParse(text, out var value))
{
_diagnostics.Add($"The number {_text} isn't valid Int32.");
}
return(new SyntaxToken(SyntaxKind.NumberToken, start, text, value));
}
if (char.IsWhiteSpace(Current))
{
var start = _position;
while (char.IsWhiteSpace(Current))
{
Next();
}
var length = _position - start;
var text = _text.Substring(start, length);
return(new SyntaxToken(SyntaxKind.WhitespaceToken, start, text, null));
}
if (char.IsLetter(Current))
{
var start = _position;
while (char.IsLetter(Current))
{
Next();
}
var length = _position - start;
var text = _text.Substring(start, length);
var kind = SyntaxFacts.GetKeywordKind(text);
return(new SyntaxToken(kind, start, text, null));
}
switch (Current)
{
case '+':
return(new SyntaxToken(SyntaxKind.PlusToken, _position++, "+", null));
case '-':
return(new SyntaxToken(SyntaxKind.MinusToken, _position++, "-", null));
case '*':
return(new SyntaxToken(SyntaxKind.StarToken, _position++, "*", null));
case '/':
return(new SyntaxToken(SyntaxKind.SlashToken, _position++, "/", null));
case '(':
return(new SyntaxToken(SyntaxKind.OpenParenthesisToken, _position++, "(", null));
case ')':
return(new SyntaxToken(SyntaxKind.CloseParenthesisToken, _position++, ")", null));
case '&':
if (Lookahead == '&')
{
return(new SyntaxToken(SyntaxKind.AmpersandAmpersandToken, _position += 2, "&&", null));
}
break;
case '|':
if (Lookahead == '|')
{
return(new SyntaxToken(SyntaxKind.PipePipeToken, _position += 2, "||", null));
}
break;
case '=':
if (Lookahead == '=')
{
return(new SyntaxToken(SyntaxKind.EqualsEqualsToken, _position += 2, "==", null));
}
break;
case '!':
if (Lookahead == '=')
{
return(new SyntaxToken(SyntaxKind.BangEqualsToken, _position += 2, "!=", null));
}
else
{
return(new SyntaxToken(SyntaxKind.BangToken, _position++, "!", null));
}
}
_diagnostics.Add($"ERROR: bad character input: '{Current}'");
return(new SyntaxToken(SyntaxKind.BadToken, _position++, _text.Substring(_position - 1, 1), null));
}
internal SyntaxToken Lex()
{
_start = _position;
_kind = SyntaxKind.BadToken;
_value = null;
switch (Current)
{
case '\0':
{
_kind = SyntaxKind.EndOfFileToken;
break;
}
case '+':
{
MoveNext();
_kind = SyntaxKind.PlusToken;
break;
}
case '-':
{
MoveNext();
_kind = SyntaxKind.MinusToken;
break;
}
case '*':
{
MoveNext();
_kind = SyntaxKind.StarToken;
break;
}
case '/':
{
MoveNext();
_kind = SyntaxKind.ForwardSlashToken;
break;
}
case '(':
{
MoveNext();
_kind = SyntaxKind.OpenParenthesisToken;
break;
}
case ')':
{
MoveNext();
_kind = SyntaxKind.CloseParenthesisToken;
break;
}
case '{':
{
MoveNext();
_kind = SyntaxKind.OpenBraceToken;
break;
}
case '}':
{
MoveNext();
_kind = SyntaxKind.CloseBraceToken;
break;
}
case '~':
{
MoveNext();
_kind = SyntaxKind.TildeToken;
break;
}
case '^':
{
MoveNext();
_kind = SyntaxKind.HatToken;
break;
}
case '!':
{
if (LookAhead == '=')
{
MoveNext(2);
_kind = SyntaxKind.BangEqualsToken;
}
else
{
MoveNext();
_kind = SyntaxKind.BangToken;
}
break;
}
case '&':
{
if (LookAhead == '&')
{
MoveNext(2);
_kind = SyntaxKind.AndAndToken;
}
else
{
MoveNext();
_kind = SyntaxKind.AndToken;
}
break;
}
case '|':
{
if (LookAhead == '|')
{
MoveNext(2);
_kind = SyntaxKind.PipePipeToken;
}
else
{
MoveNext();
_kind = SyntaxKind.PipeToken;
}
break;
}
case '=':
{
if (LookAhead == '=')
{
MoveNext(2);
_kind = SyntaxKind.EqualsEqualsToken;
}
else
{
MoveNext();
_kind = SyntaxKind.EqualsToken;
}
break;
}
case '<':
{
if (LookAhead == '=')
{
MoveNext(2);
_kind = SyntaxKind.LessOrEqualsToken;
}
else
{
MoveNext();
_kind = SyntaxKind.LessToken;
}
break;
}
case '>':
{
if (LookAhead == '=')
{
MoveNext(2);
_kind = SyntaxKind.GreaterOrEqualsToken;
}
else
{
MoveNext();
_kind = SyntaxKind.GreaterToken;
}
break;
}
case '"':
{
ReadString();
break;
}
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
{
ReadNumbersToken();
break;
}
case ' ':
case '\t':
{
ReadWhitespaceTokens();
break;
}
default:
{
if (char.IsLetter(Current))
{
ReadLettersToken();
}
else if (char.IsWhiteSpace(Current))
{
ReadWhitespaceTokens();
}
else
{
_diagnostics.ReportBadCharacter(_position, Current);
MoveNext();
}
break;
}
}
{
var text = SyntaxFacts.GetText(_kind);
var length = _position - _start;
if (text is null)
{
text = _text.ToString(_start, length);
}
return(new SyntaxToken(_kind, _start, text, _value));
}
void ReadNumbersToken()
{
do
{
MoveNext();
}while (char.IsDigit(Current));
var length = _position - _start;
var text = _text.ToString(_start, length);
if (!int.TryParse(text, out var value))
{
_diagnostics.ReportInvalidNumber(new TextSpan(_start, length), text, TypeSymbol.Int);
}
_kind = SyntaxKind.NumberToken;
_value = value;
}
void ReadLettersToken()
{
do
{
MoveNext();
}while (char.IsLetter(Current));
var text = _text.ToString(_start, _position - _start);
_kind = SyntaxFacts.GetKeywordKind(text);
}
void ReadWhitespaceTokens()
{
do
{
MoveNext();
}while (char.IsWhiteSpace(Current));
_kind = SyntaxKind.WhiteSpaceToken;
}
void ReadString()
{
MoveNext();
var done = false;
var builder = new StringBuilder();
while (!done)
{
switch (Current)
{
case '\0':
case '\r':
case '\n':
var span = new TextSpan(_start, 1);
Diagnostics.ReportUnterminatedString(span);
done = true;
break;
case '\\':
{
if (LookAhead == '"')
{
MoveNext();
}
builder.Append(Current);
MoveNext();
break;
}
case '"':
{
done = true;
MoveNext();
break;
}
default:
{
builder.Append(Current);
MoveNext();
break;
}
}
}
_kind = SyntaxKind.StringToken;
_value = builder.ToString();
}
}