private static Factor ParseFactor(Tree tree, Token token, Token[] tokens, ref int index)
{
if (token is Identifier)
{
var node = new ebnf.Nodes.Identifier {
Value = token.Value
};
return(node);
}
if (token is Literal)
{
var node = new Terminal {
Value = token.Value
};
return(node);
}
if (token is Operator && token.Value.Equals("("))
{
token = NextToken(tokens, ref index);
var node = new Grouping
{
Expression = ParseExpression(tree, ref token, tokens, ref index, ')')
};
if (!(token is Operator) || !token.Value.Equals(")"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingGrouping));
}
return(node);
}
if (token is Operator && token.Value.Equals("["))
{
token = NextToken(tokens, ref index);
var node = new Option
{
Expression = ParseExpression(tree, ref token, tokens, ref index, ']')
};
if (!(token is Operator) || !token.Value.Equals("]"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingOption));
}
return(node);
}
if (token is Operator && token.Value.Equals("{"))
{
token = NextToken(tokens, ref index);
var node = new Repetition
{
Expression = ParseExpression(tree, ref token, tokens, ref index, '}')
};
if (!(token is Operator) || !token.Value.Equals("}"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingRepetition));
}
return(node);
}
if (token is Operator && token.Value.Equals("?"))
{
token = NextToken(tokens, ref index);
var node = new SpecialSequence
{
Expression = ParseExpression(tree, ref token, tokens, ref index, '?')
};
if (!(token is Operator) || !token.Value.Equals("?"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingSpecialSequence));
}
return(node);
}
tree.Errors.Add(CreateError(token, string.Format(ErrorStrings.ExpectedFactor, token == null ? "nothing" : token.Value)));
return(null);
}
private static Factor ParseFactor(Tree tree, Token token, Token[] tokens, ref int index)
{
if(token is Identifier)
{
var node = new ebnf.Nodes.Identifier {Value = token.Value};
return node;
}
if(token is Literal)
{
var node = new Terminal { Value = token.Value };
return node;
}
if(token is Operator && token.Value.Equals("("))
{
token = NextToken(tokens, ref index);
var node = new Grouping
{
Expression = ParseExpression(tree, ref token, tokens, ref index, ')')
};
if(!(token is Operator) || !token.Value.Equals(")"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingGrouping));
}
return node;
}
if (token is Operator && token.Value.Equals("["))
{
token = NextToken(tokens, ref index);
var node = new Option
{
Expression = ParseExpression(tree, ref token, tokens, ref index, ']')
};
if (!(token is Operator) || !token.Value.Equals("]"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingOption));
}
return node;
}
if (token is Operator && token.Value.Equals("{"))
{
token = NextToken(tokens, ref index);
var node = new Repetition
{
Expression = ParseExpression(tree, ref token, tokens, ref index, '}')
};
if (!(token is Operator) || !token.Value.Equals("}"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingRepetition));
}
return node;
}
if (token is Operator && token.Value.Equals("?"))
{
token = NextToken(tokens, ref index);
var node = new SpecialSequence
{
Expression = ParseExpression(tree, ref token, tokens, ref index, '?')
};
if (!(token is Operator) || !token.Value.Equals("?"))
{
tree.Errors.Add(CreateError(token, ErrorStrings.HangingSpecialSequence));
}
return node;
}
tree.Errors.Add(CreateError(token, string.Format(ErrorStrings.ExpectedFactor, token == null ? "nothing" : token.Value)));
return null;
}