CODEWITHSUNDEEP
objective-cdata-structureshistogrammultimapbag
Michael Gaylord
Michael Gaylord

Reputation: 7312

Objective-C implementation of a histogram or bag datastructure

Instead of implementing my own I was wondering if anyone knows of a histogram or bag datastructure implementation in Objective-C that I can use.

Essentially a histogram is a hashmap of lists where the lists contain values that relate to their hash entry. A good example is a histogram of supermarket items where you place each group of items dairy, meat, canned goods in their own bag. You can then very easily access each group of items according to their type.

Upvotes: 3

Views: 2545

Answers (4)

fatuhoku
fatuhoku

Reputation: 4911

CFIOMultimap apparently is an implementation of a multimap. However, as of the time of writing I couldn't get it to work. It returns nils all the time when I subscript.

Perhaps it can be fixed and adapted for your use.

Upvotes: 0

Quinn Taylor
Quinn Taylor

Reputation: 44769

NSCountedSet is a multiset (aka "bag") that counts distinct objects, but doesn't allow duplicates. However, based on your explanation, I don't think that's what you need, and neither is a histogram, which automatically buckets values based on a set of (usually numerical) ranges.

I believe what you really want is a multimap, which is a "key to one-or-more values" relation. The data structures framework I maintain includes CHMultiDictionary, a multimap implementation. I won't claim by any means that it's perfect or complete, but I hope it may be helpful for your problem.

Upvotes: 5

Peter N Lewis
Peter N Lewis

Reputation: 17811

It sounds to me like you simply want a dictionary of arrays. You can put NSArrays as elements of NSDictionarys, something like:

NSMutableDictionary* dict = [NSMutableDictionary dictionary];
[dict setObject:[NSMutableArray arrayWithObjects:@"milk", @"eggs", @"cheese", nil] forKey:@"dairy"];
[dict setObject:[NSMutableArray arrayWithObjects:@"steak", @"sausages", @"mince", nil] forKey:@"meat"];

[[dict objectForKey:@"meat"] addObject:@"lamb"];

NSLog( @"Dictionary is %@", dict );

Upvotes: 3

Alex Martelli
Alex Martelli

Reputation: 882391

There's one in the GNU Objective-C Class library, but the docs appear to be pretty incomplete and the project's homepage must be currently having a problem -- still, if GPL software is acceptable for your project, you might want to download and check the sources.

Upvotes: 1

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