private static StateMonad <TState, Tree <Tuple <TState, TContents> > > MakeMonad(
Tree <TContents> t,
Func <StateMonad <TState, TState> > incrementer)
{
if (t is Leaf <TContents> )
{
var lf = (t as Leaf <TContents>);
return(incrementer()
.Bind(n => StateMonad <TState, Tree <Tuple <TState, TContents> > >
.Return(new Leaf <Tuple <TState, TContents> >(Tuple.Create(n, lf.Contents)))));
}
if (t is Branch <TContents> )
{
var br = (t as Branch <TContents>);
var oldleft = br.Left;
var oldright = br.Right;
return(MakeMonad(oldleft, incrementer)
.Bind(newleft => MakeMonad(oldright, incrementer)
.Bind(newright => StateMonad <TState, Tree <Tuple <TState, TContents> > >
.Return(new Branch <Tuple <TState, TContents> >(newleft, newright)))));
}
throw new Exception("MakeMonad/MLabel: impossible Tree subtype");
}
public static StateMonad <TState, TContentsB> Bind <TContentsB>(
StateMonad <TState, TContents> inputMonad,
Func <TContents, StateMonad <TState, TContentsB> > inputMaker)
{
return(new StateMonad <TState, TContentsB>(state0 =>
{
var lcp1 = inputMonad.StateMaker(state0);
var state1 = lcp1.First;
var contents1 = lcp1.Second;
return inputMaker(contents1).StateMaker(state1);
}));
}