public override RecursionResult <KObject> Combine(KObject args, KEnvironment env, Continuation <KObject> cont)
{
var res = CheckParameter(args, 3, "guard-continuation");
if (res != null)
{
return(CPS.Error(res, cont));
}
KContinuation c = Second(args) as KContinuation;
KObject entry = First(args);
KObject exit = Third(args);
try
{
if (null == c)
{
throw new RuntimeException("guard-continuation: not a continution");
}
c.Value.EntryGuard = assignGuards(entry);
c.Value.ExitGuard = assignGuards(exit);
return(CPS.Return(c, cont));
}
catch (Exception e)
{
return(CPS.Error(e.Message, cont));
}
}
private List <KGuard> assignGuards(KObject clauses)
{
List <KGuard> result = new List <KGuard>();
if (clauses is KPair)
{
KPair.Foreach(x =>
{
int length = KPair.Length(x);
if (length == 2)
{
KContinuation selector = First(x) as KContinuation;
KApplicative interceptor = Second(x) as KApplicative;
if (selector == null || interceptor == null)
{
throw new RuntimeException("guard-continuation: invalid clause, wrong types");
}
result.Add(new KGuard {
Selector = selector, Interceptor = interceptor
});
}
else
{
throw new RuntimeException("guard-continuation: invalid clause");
}
}, clauses);
}
return(result);
}
public override object Do(KObject args, KEnvironment env, Continuation <KObject> cont)
{
CPara(args, 1);
KContinuation c = First(args) as KContinuation;
Check(c, "expected continuation");
return(new KApplicative(new PPassCont(c)));
}
public override RecursionResult <KObject> Combine(KObject args, KEnvironment env, Continuation <KObject> cont)
{
int len = KPair.Length(args);
if (len < 2 || len > 3)
{
return(CPS.Error("extend-continuation: argument mismatch", cont));
}
KContinuation argC = First(args) as KContinuation;
KApplicative argA = Second(args) as KApplicative;
KEnvironment argE = len == 3 ? Third(args) as KEnvironment : new KEnvironment();
if (argC == null || argA == null || argE == null)
{
return(CPS.Error("extend-continuation: mismatching arguments", cont));
}
var nc = new Continuation <KObject>((val, ctxt) =>
{
return(CPS.Next(() => Evaluator.rceval(new KPair(argA.Combiner, val, true), argE, argC.Value), argC.Value));
}, argC.Value, argA);
return(Return(new KContinuation(nc), cont));
}
public PPassCont(KContinuation c)
{
myc = c;
}