public static U Fold <T, U>(this Maybe <T> ts, U identity, Func <U, T, U> fn)
{
var accumulator = identity;
foreach (T element in ts.AsEnumerable())
{
accumulator = fn(accumulator, element);
}
return(accumulator);
}
public static void ForEach <A>(this Maybe <A> @this, Action <A> f) => @this.AsEnumerable().ForEach(f);
