private void HandleString()
{
while (Peek() != '"' && !IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
Advance();
}
if (IsAtEnd())
{
// we've hit the end before we found the closing quotes
CsLox.Error(line, "Unterminated string");
return;
}
// consume the closing quotes
Advance();
// trim the surrounding quotes away
string value = source.Substring(start + 1, current - 1);
AddToken(TokenType.String, value);
}
private void ScanToken()
{
char c = Advance();
switch (c)
{
case '(': AddToken(TokenType.LeftParen); break;
case ')': AddToken(TokenType.RightParen); break;
case '{': AddToken(TokenType.LeftBrace); break;
case '}': AddToken(TokenType.RightBrace); break;
case ',': AddToken(TokenType.Comma); break;
case '.': AddToken(TokenType.Dot); break;
case '-': AddToken(TokenType.Minus); break;
case '+': AddToken(TokenType.Plus); break;
case ';': AddToken(TokenType.Semicolon); break;
case '*': AddToken(TokenType.Star); break;
case '!': AddToken(FollowedBy('=') ? TokenType.BangEqual : TokenType.Bang); break;
case '=': AddToken(FollowedBy('=') ? TokenType.EqualEqual : TokenType.Equal); break;
case '<': AddToken(FollowedBy('=') ? TokenType.LessEqual : TokenType.Less); break;
case '>': AddToken(FollowedBy('=') ? TokenType.GreaterEqual : TokenType.Greater); break;
case '/':
if (FollowedBy('/'))
{
// a comment goes until the end of the line
while (Peek() != '\n' && !IsAtEnd())
{
Advance();
}
}
else
{
AddToken(TokenType.Slash);
}
break;
case ' ':
case '\r':
case '\t':
// ignore whitespaces
break;
case '\n':
line++;
break;
case '"': HandleString(); break;
default:
if (IsDigit(c))
{
HandleNumber();
}
else if (IsAlpha(c))
{
HandleIdentifier();
}
else
{
CsLox.Error(line, $"Unexpected character '{c}'.");
}
break;
}
}