private static State <IReadOnlyList <TA>, BinTree> Build2 <TA>(int n)
{
if (n == 1)
{
return(State <IReadOnlyList <TA> > .Get().Bind(xs =>
{
var head = xs.First();
var tail = (IReadOnlyList <TA>)xs.Skip(1).ToList();
return State <IReadOnlyList <TA> > .Put(tail).Bind(_ =>
{
BinTree leaf = new Leaf <TA>(head);
return State <IReadOnlyList <TA> > .Return(leaf);
});
}));
}
var m = n / 2;
return(Build2 <TA>(m).Bind(
u => Build2 <TA>(n - m).Bind(
v =>
{
BinTree fork = new Fork(u, v);
return State <IReadOnlyList <TA> > .Return(fork);
})));
}
private static State <Tuple <IReadOnlyList <TA>, int>, BinTree> Build2 <TA>(int n)
{
if (n == 1)
{
return(State <Tuple <IReadOnlyList <TA>, int> > .Get().Bind(
s1 =>
{
var xs = s1.Item1;
var index = s1.Item2;
var s2 = Tuple.Create(xs, index + 1);
var head = xs[index];
BinTree leaf = new Leaf <TA>(head);
return State <Tuple <IReadOnlyList <TA>, int> > .Put(s2).BindIgnoringLeft(
State <Tuple <IReadOnlyList <TA>, int> > .Return(leaf));
}));
}
var m = n / 2;
return(Build2 <TA>(m).Bind(
u => Build2 <TA>(n - m).Bind(
v =>
{
BinTree fork = new Fork(u, v);
return State <Tuple <IReadOnlyList <TA>, int> > .Return(fork);
})));
}
private static Tuple <BinTree, IReadOnlyList <TA> > Build2 <TA>(int n, IReadOnlyList <TA> xs)
{
if (n == 1)
{
var head = xs.First();
var tail = (IReadOnlyList <TA>)xs.Skip(1).ToList();
BinTree leaf = new Leaf <TA>(head);
return(Tuple.Create(leaf, tail));
}
var m = n / 2;
var t1 = Build2(m, xs);
var u = t1.Item1;
var xs1 = t1.Item2;
var t2 = Build2(n - m, xs1);
var v = t2.Item1;
var xs2 = t2.Item2;
BinTree fork = new Fork(u, v);
return(Tuple.Create(fork, xs2));
}
private static Tuple <BinTree, Tuple <IReadOnlyList <TA>, int> > Build2 <TA>(int n, Tuple <IReadOnlyList <TA>, int> state)
{
if (n == 1)
{
var xs = state.Item1;
var index = state.Item2;
var head = xs[index];
BinTree leaf = new Leaf <TA>(head);
return(Tuple.Create(leaf, Tuple.Create(xs, index + 1)));
}
var m = n / 2;
var t1 = Build2(m, state);
var u = t1.Item1;
var state1 = t1.Item2;
var t2 = Build2(n - m, state1);
var v = t2.Item1;
var state2 = t2.Item2;
BinTree fork = new Fork(u, v);
return(Tuple.Create(fork, state2));
}