[Haskell-cafe] Haskell-Cafe Digest, Vol 90, Issue 48

[Louis Wasserman]

>
> Another common usage for Map is as a functional integer-indexed
> random access array.
> Once I implemented the standard algorithm for random shuffle
> of a list using Data.Map Int. It was much nicer than the STArray
> version, in my opinion. But when I tried switching to Data.IntMap,
> hoping to make it faster, I was devastatingly disappointed. Now
> I understand why.


A couple thoughts:

If you're going to provide an isSingleton method, provide

getSingleton :: IntMap m -> Maybe (Int, a)

which is trivial based on the current implementation.

For my TrieMap package, I've been working on my WordMap implementation
here<http://hackage.haskell.org/packages/archive/TrieMap/3.0.1/doc/html/src/Data-TrieMap-WordMap.html>.
 (Using Words as keys makes my life easier, and it doesn't take too much
work to write a wrapper that provides an order-preserving bijection from Int
to Word.)  It provides O(1) size, but its design reflects my willingness to
trade memory and code size for speed. ;)

Louis Wasserman
wasserman.louis at gmail.com
http://profiles.google.com/wasserman.louis
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