private static GraphZipper <T> GoDown <T>(GraphZipper <T> zipper)
{
if (zipper == null || !zipper.Focus.Children.Any())
{
return(null);
}
var focus = zipper.Focus;
var children = focus.Children;
var newCrumb = new GraphCrumb <T>(focus.Value, Enumerable.Empty <Graph <T> >(), children.Skip(1));
return(new GraphZipper <T>(children.First(), new[] { newCrumb }.Concat(zipper.Crumbs)));
}
private static GraphZipper <T> GoRight <T>(GraphZipper <T> zipper)
{
if (zipper == null || !zipper.Crumbs.Any() || !zipper.Crumbs.First().Right.Any())
{
return(null);
}
var crumbs = zipper.Crumbs;
var firstCrumb = crumbs.First();
var newCrumb = new GraphCrumb <T>(firstCrumb.Value, firstCrumb.Left.Concat(new[] { zipper.Focus }), firstCrumb.Right.Skip(1));
return(new GraphZipper <T>(firstCrumb.Right.First(), new[] { newCrumb }.Concat(crumbs.Skip(1))));
}
