Re: How do you use BinaryHeap with Array (or just make a growable heap)?
On 2011-03-28 20:24:55 +0200, Jonathan M Davis said: Well, Array definitely shouldn't be a random access range. The range for it (which you'd typically get by slicing it) would be random access, but the container itself isn't a range of any kind. Containers aren't ranges (barring the oddities of dynamic arrays). I've never used BinaryHeap, but glancing at it, my guess would be that the correct solution (if you want to use Array with it) is to create an Array and then pass its range to heapify: Array!uint a; //... put stuff in a. auto heap = heapify(a[]); I'm not sure if that's growable or not though. Hm. I can't even get the slicing to work: /path/to/phobos/std/container.d(2436): Error: function std.container.Array!(uint).Array.Range.opSlice (uint a, uint b) is not callable using argument types () Glancing at BinaryHeap, it'll work with arrays though, so you don't need to use Array. Hm. The docs say "If Store is a range, the BinaryHeap cannot grow beyond the size of that range. If Store is a container that supports insertBack, the BinaryHeap may grow by adding elements to the container." So it seems that a container (such as Array, which has insertBack) should be usable, according to the docs. And an array/slice would not be growable. (At least, it isn't growable in practice.) See also: http://www.digitalmars.com/d/archives/digitalmars/D/std.algorithm.BinaryHeap_88811.html What I'm looking for is a completely standard priority queue, where I can add and remove objects, and not have to know the maximum size beforehand. I'd also like to have tuple entries, but it seems that BinaryHeap has trouble with that as well... I don't know what the ideal container to use with a BinaryHeap is though. Also, in my experience, Array is pretty buggy at this point, so I'm not sure how far you'll get with it. Yeah, it seems to be. At the moment, I've just reimplemented BinaryHeap myself (with a subset of the Phobos API), so that it can handle arrays of tuples (which I couldn't get std.container.BinaryHeap to accept). I then wrapped it in a PriorityQueue class, which takes care of resizing the array (and having BinaryHeap switch to the possibly reallocated new one). Not an ideal solution, but at least it works. -- Magnus Lie Hetland http://hetland.org
Re: How do you use BinaryHeap with Array (or just make a growable heap)?
On 2011-03-28 05:35, Magnus Lie Hetland wrote: > I need a (growable) binary heap, and I'm trying to avoid writing one > myself (which isn't too hard, of course :) ... but for some reason I > can't figure out how to use Phobos to do it. > > I've seen stated (e.g., by Andrei and in the docs) that the standard > way is combining BinaryHeap with an Array. Which is fine with me. > Except I can't make it work. E.g., I try: > > Array!uint A; > auto Q = heapify(A); > > The error is > > /path/to/phobos/std/container.d(2658): Error: template instance > BinaryHeap!(Array!(uint)) does not match template declaration > BinaryHeap(Store,alias less = "a < b") if (isRandomAccessRange!(Store) > > || isRandomAccessRange!(typeof(Store.init[]))) > > /path/to/phobos/std/container.d(2658): Error: BinaryHeap!(Array!(uint)) > is used as a type > > When I check it out, it seems that isRandomAccessRange!(Array!uint) > returns false (and it doesn't, AFAIK, have an init), which means that > the error makes sense. > > Does this mean... > > 1. That Array isn't, and shouldn't be, a random access range? > 2. That Array can't, and shouldn't be (despite official statements to > the contrary) be used with BinaryHeap? > > (I suspect the answer to both is "you're doing it wrong" ;) > > And, of course, my main question: > > 3. How do you (canonically) make a growable heap using Phobos? Well, Array definitely shouldn't be a random access range. The range for it (which you'd typically get by slicing it) would be random access, but the container itself isn't a range of any kind. Containers aren't ranges (barring the oddities of dynamic arrays). I've never used BinaryHeap, but glancing at it, my guess would be that the correct solution (if you want to use Array with it) is to create an Array and then pass its range to heapify: Array!uint a; //... put stuff in a. auto heap = heapify(a[]); I'm not sure if that's growable or not though. Glancing at BinaryHeap, it'll work with arrays though, so you don't need to use Array. I don't know what the ideal container to use with a BinaryHeap is though. Also, in my experience, Array is pretty buggy at this point, so I'm not sure how far you'll get with it. - Jonathan M Davis
