/// <summary>
/// Get all the allowed permutations of child nodes.
/// </summary>
private static IEnumerable <List <ParseTreeNode> > AllowedChildPermutations(ParseTreeNode pt)
{
// Check if pt is a commutative binop operation
if (ExcelFormulaParser.IsBinaryOperation(pt) &&
_communativeBinOps.Contains(ExcelFormulaParser.GetFunction(pt)))
{
var reversed = new List <ParseTreeNode>(pt.ChildNodes);
reversed.Reverse();
return(new[] { pt.ChildNodes, reversed });
}
else
{
// Only original childnodes order allowed
return(Enumerable.Repeat(pt.ChildNodes, 1));
}
}