On 3/18/18 8:34 AM, Viktor wrote:
Hey,
I'm trying to convert an old legacy app to D and have a couple of
questions. It has been a very fun weekend!
First, I could not make std.container.rbtree use a delegate for a
comparator. The docs say it should be possible, but I got a weird error.
I tracked it down to RedBlackTreee.opEquals() using explicit function
when calling equals():
return equal!(function(Elem a, Elem b) => !_less(a,b) &&
!_less(b,a))(thisRange, thatRange);
When I removed the "function" things started compiling (I have yet to
test the code due to question #2 below). I've done a dub -b unittest
without issues so it might be OK.
So, the first...several questions are: do you think this change is safe
and should I raise an issue in the bugzilla or do a PR for it on github?
Yes, seems like an oversight. RedBlackTree.opEquals was added almost 6
years ago, and it's possible this wouldn't have worked back then
(https://github.com/dlang/phobos/pull/900)
Should it include a new unittest that makes sure rbtree can be
instantiated with a delegate?
Definitely. Thanks for thinking of this!
The other part I'm still struggling with is about auto types. Can I
store the rbtree type in the following class so it can be used from
another method?
class Indexer(T, alias pred)
{
alias RBType = RedBlackTree!(uint, (a, b) => comp(a, b));
this(T storage)
{
this.storage = storage;
this.index = new RBType();
}
void dumpIndex()
{
// how to get my dirty hands on the index here?
// answer: just use it?
}
bool comp(uint i1, uint i2)
{
auto rec1 = storage[i1];
auto rec2 = storage[i2];
return pred(rec1, rec2);
}
private T storage;
RBType index;
}
-Steve
