private Ast WhileLoop()
{
if (!_tokenStream.IsMatch <WhileToken>())
{
return(null);
}
WhileToken token = _tokenStream.Take <WhileToken>();
_tokenStream.Take <LeftParensToken>();
Ast condition = Expression();
if (condition == null)
{
throw new InvalidSyntaxException("Condition of while-loop must be an expression", _tokenStream.Current.Position, null);
}
_tokenStream.Take <RightParensToken>();
Ast body = Statement();
if (body == null)
{
throw new InvalidSyntaxException("While-loop must have a body statement", _tokenStream.Current.Position, null);
}
return(new WhileLoop(token, condition, body.ToScope()));
}
public Token GetToken()
{
State = LexicAnalyserState.Initial;
Value = HasNext ? Character.ToString() : "";
Token token = null;
while (HasNext && token == null)
{
switch (State)
{
case LexicAnalyserState.Initial:
HandleInitial();
break;
case LexicAnalyserState.NonTerminal:
token = new NonTerminalToken(Value);
CurrentIndex++;
break;
case LexicAnalyserState.Space:
token = new SpaceToken();
CurrentIndex++;
break;
case LexicAnalyserState.Terminal:
token = new TerminalToken(Value);
CurrentIndex++;
break;
case LexicAnalyserState.Empty:
token = new EmptyToken();
CurrentIndex++;
break;
case LexicAnalyserState.NewLine:
token = new NewLineToken(Value);
CurrentIndex++;
break;
case LexicAnalyserState.Identifier:
token = new IdentifierToken(Value);
CurrentIndex++;
break;
case LexicAnalyserState.Number:
token = new NumberToken(Value);
CurrentIndex++;
break;
case LexicAnalyserState.Var:
token = new VarToken();
CurrentIndex++;
break;
case LexicAnalyserState.Write:
token = new WriteToken();
CurrentIndex++;
break;
case LexicAnalyserState.Read:
token = new ReadToken();
CurrentIndex++;
break;
case LexicAnalyserState.If:
token = new IfToken();
CurrentIndex++;
break;
case LexicAnalyserState.End:
token = new EndToken();
CurrentIndex++;
break;
case LexicAnalyserState.Then:
token = new ThenToken();
CurrentIndex++;
break;
case LexicAnalyserState.Begin:
token = new BeginToken();
CurrentIndex++;
break;
case LexicAnalyserState.While:
token = new WhileToken();
CurrentIndex++;
break;
case LexicAnalyserState.Do:
token = new DoToken();
CurrentIndex++;
break;
case LexicAnalyserState.SemiColon:
token = new SemiColonToken();
CurrentIndex++;
break;
case LexicAnalyserState.OpenParentheses:
token = new OpenParenthesesToken();
CurrentIndex++;
break;
case LexicAnalyserState.CloseParentheses:
token = new CloseParenthesesToken();
CurrentIndex++;
break;
case LexicAnalyserState.Plus:
token = new PlusToken();
CurrentIndex++;
break;
case LexicAnalyserState.Sub:
token = new SubToken();
CurrentIndex++;
break;
case LexicAnalyserState.Great:
token = new GreatToken();
CurrentIndex++;
break;
case LexicAnalyserState.Less:
token = new LessToken();
CurrentIndex++;
break;
case LexicAnalyserState.Equal:
token = new EqualToken();
CurrentIndex++;
break;
case LexicAnalyserState.Repeat:
token = new RepeatToken();
CurrentIndex++;
break;
case LexicAnalyserState.Until:
token = new UntilToken();
CurrentIndex++;
break;
case LexicAnalyserState.Attribution:
token = new AttributionToken();
CurrentIndex++;
break;
case LexicAnalyserState.NotEqual:
token = new NotEqualToken();
CurrentIndex++;
break;
case LexicAnalyserState.GreatOrEqual:
token = new GreatOrEqualToken();
CurrentIndex++;
break;
case LexicAnalyserState.LessOrEqual:
token = new LessOrEqualToken();
CurrentIndex++;
break;
default:
throw new ArgumentOutOfRangeException();
}
}
return(token);
}
