private Element Rearrange(AssignmentElement root, Element targetVar)
{
while (true)
{
// Check for no rearrange necessary
if (root.Elements.Lhs == targetVar) return root.Elements.Rhs;
// Rearrange first part of tree
var targetPath = root.Elements.Lhs.FindPath(targetVar).ToArray();
var lastOperation = targetPath.First();
var varBranch = targetPath.Skip(1).FirstOrDefault() ?? targetVar;
var newRoot = root.Replace(lastOperation, varBranch) as AssignmentElement;
var inversion = lastOperation.Invert(varBranch, newRoot.Elements.Rhs);
root = newRoot.Replace(newRoot.Elements.Rhs, inversion) as AssignmentElement;
}
}
