public override Production Parse(List <Token> tokens)
{
var nonWhitespace = tokens.NextNonWhitespace();
if (nonWhitespace.TokenClass != TokenClass.Boolean &&
nonWhitespace.TokenClass != TokenClass.Float &&
nonWhitespace.TokenClass != TokenClass.Integer &&
nonWhitespace.TokenClass != TokenClass.ReplacementSymbol &&
nonWhitespace.TokenClass != TokenClass.StartScope &&
nonWhitespace.TokenClass != TokenClass.String &&
nonWhitespace.TokenClass != TokenClass.Symbol)
{
return(new Production(null, tokens));
}
var remainder = tokens.ToList();
while (remainder.Any() && Constituents.Count < 3) // An operation must have exactly three items: value op value
{
var currentToken = remainder.First().TokenClass;
Production current = null;
//check whether the right hand side of the operation is another operation
if (Constituents.Count == 2)
{
current = new OperationExpression().Parse(remainder);
}
if (Constituents.Count != 2 || current?.Expression == null)
{
switch (currentToken)
{
case TokenClass.StartScope:
current = new ScopedExpression().Parse(remainder);
break;
case TokenClass.Whitespace:
current = new WhitespaceExpression().Parse(remainder);
break;
case TokenClass.ReplacementSymbol:
current = new ReplacementSymbolExpression().Parse(remainder);
break;
case TokenClass.Symbol:
current = new FunctionExpression().Parse(remainder);
if (current.Expression == null)
{
current = new SymbolExpression().Parse(remainder);
}
break;
case TokenClass.Operator:
if (Constituents.Count == 2)
{
current = NumericExpression.TryParseNumeric(remainder);
break;
}
current = new OperatorExpression().Parse(remainder);
break;
case TokenClass.Integer:
case TokenClass.Float:
current = NumericExpression.TryParseNumeric(remainder);
break;
case TokenClass.String:
current = new StringExpression().Parse(remainder);
break;
case TokenClass.Boolean:
current = new BooleanExpression().Parse(remainder);
break;
default:
return(new Production(null, tokens));
}
}
if (current == null || current.Expression == null)
{
return(new Production(null, tokens));
}
remainder = current.RemainingTokens;
if (!(current.Expression is WhitespaceExpression))
{
Constituents.Add(current.Expression);
}
}
if (Constituents.None(c => c is OperatorExpression))
{
return(new Production(null, tokens));
}
if (Constituents.Count != 3)
{
return(new Production(null, tokens));
}
return(new Production(this, remainder));
}