private static WBT <Pair <k, v> > .N Alter(Func <k, Ord> p, k key, Func <Opt <v>, Opt <v> > f, WBT <Pair <k, v> > .N t) =>
WBT <Pair <k, v> > .Tip(t)
? (f(Ctors.None())).Case(_ => WBT <Pair <k, v> > .Tip(), (v vv) => WBT <Pair <k, v> > .Singleton(Ctors.Pair(key, vv)))
: (p(t.v.Left()).Case(
_ => WBT <Pair <k, v> > .Balance(t.v, Alter(p, key, f, t.l), t.r),
_ => f(Ctors.Some(t.v.Right())).Case(
__ => WBT <Pair <k, v> > .Glue(t.l, t.r),
vv => WBT <Pair <k, v> > .Bin(t.s, Ctors.Pair(key, vv), t.l, t.r)),
_ => WBT <Pair <k, v> > .Balance(t.v, t.l, Alter(p, key, f, t.r))));
public static Pair <a, N> DeleteFindMax(N t)
{
if (Tip(t))
{
throw new InvalidOperationException("No maximum for an empty tree");
}
if (Tip(t.r))
{
return(Ctors.Pair(t.v, t.l));
}
var max = DeleteFindMax(t.r);
return(Ctors.Pair(max.Left(), BalanceL(t.v, t.l, max.Right())));
}
public static Pair <a, N> DeleteFindMin(N t)
{
if (Tip(t))
{
throw new InvalidOperationException("No minimum for an empty tree");
}
if (Tip(t.l))
{
return(Ctors.Pair(t.v, t.r));
}
var min = DeleteFindMin(t.l);
return(Ctors.Pair(min.Left(), BalanceR(t.v, min.Right(), t.r)));
}
public TreeMap <k, v> Singleton(k key, v value, ROrder <k, Unit> ord = null) => New(ord, WBT <Pair <k, v> > .Singleton(Ctors.Pair(key, value)));
private static WBT <Pair <k, v> > .N Map(Func <k, v, v> f, WBT <Pair <k, v> > .N t) => WBT <Pair <k, v> > .Tip(t) ? t : WBT <Pair <k, v> > .Bin(t.s, Ctors.Pair(t.v.Left(), t.v.Case(f)), Map(f, t.l), Map(f, t.r));