public static RecursionResult <KObject> rceval(KObject datum, KEnvironment env, Continuation <KObject> cont)
{
// useful for debugging
//Console.WriteLine(datum.Display());
if (datum is KPair)
{
KPair p = datum as KPair;
// this function get called when the operator is evaluated to f
var childCont = new Continuation <KObject>((f) =>
{
if (f is KOperative)
{
return(combineOp(f as KOperative, p.Cdr, env, cont));
}
else if (f is KApplicative && (p.Cdr is KPair || p.Cdr is KNil))
{
if (p.Cdr is KNil)
{
return(combineApp(f as KApplicative, p.Cdr, env, cont));
}
KPair ops = p.Cdr as KPair;
LinkedList <KObject> input = new LinkedList <KObject>();
KPair.Foreach(x =>
{
input.AddLast(x);
}, ops);
LinkedList <KObject> pairs = new LinkedList <KObject>();
Func <KObject, RecursionResult <KObject> > recursion = null;
bool firstRun = true;
// this continuation is called with the next argument evaled to x. Place next value
recursion = (x) =>
{
if (CPS.getContext() is int && !firstRun)
{
// restore elements when reentering continuation
int oldInputCount = (int)CPS.getContext() + 1;
input = new LinkedList <KObject>();
KPair.Foreach(e =>
{
input.AddLast(e);
}, ops);
int leaveOutputs = input.Count - oldInputCount;
while (input.Count > oldInputCount)
{
input.RemoveFirst();
}
while (pairs.Count >= leaveOutputs)
{
pairs.RemoveFirst();
}
firstRun = true;
}
pairs.AddFirst(x);
if (input.Count == 0)
{
// we are finished
KObject output = new KNil();
foreach (var el in pairs)
{
output = new KPair(el, output);
}
firstRun = false;
return(combineApp(f as KApplicative, output, env, cont));
}
else
{
// do something with the next Head argument
KObject next = input.First.Value;
input.RemoveFirst();
var cc2 = new Continuation <KObject>(recursion, cont, input.Count);
return(CPS.PassTo(() => rceval(next, env, cc2)));
}
};
KObject next2 = input.First.Value;
input.RemoveFirst();
var cc = new Continuation <KObject>(recursion, cont, input.Count);
return(CPS.PassTo(() => rceval(next2, env, cc)));
}
return(CPS.Error <KObject>("Unsuitable operation of " + f.Write(), cont));
}, cont, "eval op/app");
return(CPS.PassTo(() => rceval(p.Car, env, childCont)));
}
else if (datum is KSymbol)
{
KObject val = env.Lookup(((KSymbol)datum).Value);
if (null == val)
{
return(CPS.Error <KObject>("Unbound variable " + ((KSymbol)datum).Value, cont));
}
return(CPS.Return(val, cont));
}
else
{
return(CPS.Return(datum, cont));
}
}
