/// <summary>
/// Constructs a new parser instance
/// </summary>
/// <param name="lexer">The lexer instance</param>
public Parser(Lexer lexer)
{
this._lexer = lexer;
this._token = null;
this._hasToken = false;
}
/// <summary>
/// Retrieves the next token without consuming it
/// </summary>
/// <returns>The next token</returns>
private Token _peek()
{
if (!_hasToken)
{
_token = _lexer.Next();
_hasToken = true;
}
return _token;
}
/// <summary>
/// Reads the next token from the lexer
/// </summary>
/// <returns></returns>
public Token Next()
{
retry:
if (_eof())
return null;
char c = _peekChar();
if (Char.IsWhiteSpace(c))
{
_skipWhiteSpace();
goto retry;
}
if(c == '–')
{
// long dash, skip
_readChar();
goto retry;
}
if(Char.IsSymbol(c) || Char.IsPunctuation(c))
{
string symbol = _readSymbolString();
return _resolve(_symbolTypes, symbol, true);
}
if(Char.IsLetter(c))
{
string ident = _readIdentifierString();
var token = _resolve(_identifierTypes, ident, false);
if (token == null)
token = new Token(TokenType.Identifier, ident);
return token;
}
if (Char.IsDigit(c))
{
string number = _readInteger();
return new Token(TokenType.Integer, number);
}
throw new InvalidDataException(c.ToString());
}