private void MoveNextIfNextIsSpace(LexicAnalyserState state)
{
if (NextIsSpaceOrNewline())
{
State = state;
}
else
{
MoveNext();
}
}
private void MoveNext()
{
if (char.IsLetter(Value[0]) && NextIsSpaceOrNewline())
{
State = LexicAnalyserState.Identifier;
}
else if (Value.IsNumber() && NextIsSpaceOrNewline())
{
State = LexicAnalyserState.Number;
}
else if (NextIsSpaceOrNewline())
{
State = LexicAnalyserState.Terminal;
}
else
{
State = LexicAnalyserState.Initial;
CurrentIndex++;
if (HasNext)
{
Value += Character;
}
}
}
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);
}
private void HandleInitial()
{
if (IsNonTerminal() && NextIsSpaceOrNewline())
{
State = LexicAnalyserState.NonTerminal;
}
else if (IsSpace())
{
State = LexicAnalyserState.Space;
}
else if (IsNewLine(Value))
{
State = LexicAnalyserState.NewLine;
}
else
{
switch (Value.ToLower())
{
case "var":
MoveNextIfNextIsSpace(LexicAnalyserState.Var);
break;
case "write":
MoveNextIfNextIsSpace(LexicAnalyserState.Write);
break;
case "read":
MoveNextIfNextIsSpace(LexicAnalyserState.Read);
break;
case "if":
State = LexicAnalyserState.If;
break;
case "end":
State = LexicAnalyserState.End;
break;
case "then":
State = LexicAnalyserState.Then;
break;
case "begin":
State = LexicAnalyserState.Begin;
break;
case "while":
MoveNextIfNextIsSpace(LexicAnalyserState.While);
break;
case "do":
State = LexicAnalyserState.Do;
break;
case ";":
State = LexicAnalyserState.SemiColon;
break;
case "(":
State = LexicAnalyserState.OpenParentheses;
break;
case ")":
State = LexicAnalyserState.CloseParentheses;
break;
case "+":
State = LexicAnalyserState.Plus;
break;
case "-":
State = LexicAnalyserState.Sub;
break;
case ">":
if (NextCharacter == '=')
{
State = LexicAnalyserState.GreatOrEqual;
}
else
{
State = LexicAnalyserState.Great;
}
break;
case "<":
if (NextCharacter == '=')
{
State = LexicAnalyserState.LessOrEqual;
}
else
{
State = LexicAnalyserState.Less;
}
break;
case "=":
State = LexicAnalyserState.Equal;
break;
case "!=":
State = LexicAnalyserState.NotEqual;
break;
case "ε":
State = LexicAnalyserState.Empty;
break;
case "repeat":
MoveNextIfNextIsSpace(LexicAnalyserState.Repeat);
break;
case "until":
State = LexicAnalyserState.Until;
break;
case ":=":
State = LexicAnalyserState.Attribution;
break;
default:
MoveNext();
break;
}
}
}
