private Either <IParseState> _CreateExpression(IParseState OldState, IParseState NewState)
{
var t_Attempt = m_CreateExpression
.Select(F => _AttemptCreate(F, OldState, NewState))
.FirstOrDefault(E => !E.HasError());
return(t_Attempt == null ?
new Exception("Unable to match any expression creation function") :
t_Attempt.HasError() ?
t_Attempt.Error :
new Either <IParseState>(
NewState.ToCopy(NewState.Tokens, OldState.Expressions.Append(t_Attempt.Value))
));
}
protected virtual Either<IParseState> _PopAndMatch(Stack<Token> PatternTokens, IParseState State)
{
var t_CurrentTokens = State.Tokens;
var t_MatchedTokens = new List<Token>();
while (PatternTokens.Count != 0)
{
var t_PatternToken = PatternTokens.Pop();
var t_Token = t_CurrentTokens.Pop();
if (!_CompareTokens(t_PatternToken, t_Token))
return new Exception("Pattern Tokens do not match input Tokens.",
new Exception($"Expected: {t_PatternToken.Type} {t_PatternToken.Text} Found: {t_Token.Type} {t_Token.Text}"));
t_MatchedTokens.Add(t_Token);
}
var t_CreatedExpression = _CreateExpression(t_MatchedTokens);
return t_CreatedExpression.HasError() ?
new Either<IParseState>(new Exception("No Tokens Matched")) :
new Either<IParseState>(State.ToCopy(t_CurrentTokens, State.Expressions.Append(t_CreatedExpression.Value)));
}