Re: [Haskell-cafe] Announce: EnumMap-0.0.1

EnumMap silently passes this responsibility to the user, without even a note in the documentation.

Like I've said, I made no modifications to the documentation other than replacing IntMap with EnumMap. Should the community show more interest in the EnumMap, such a change will show up in the docs. On Wed, Aug 12, 2009 at 12:58 PM, David Menendez wrote:

On Wed, Aug 12, 2009 at 12:07 PM, John Van Enk wrote:

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On Wed, Aug 12, 2009 at 11:34 AM, David Menendez wrote:

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On Wed, Aug 12, 2009 at 9:16 AM, John Van Enk wrote:

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On Wed, Aug 12, 2009 at 2:09 AM, Ketil Malde wrote:

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And perhaps also note that you will get exceptions for values outside the Enum range.

I'd think that part is obvious.

That depends on what "outside the Enum range" means. You'll get an exception if you somehow get an Int key in the map which doesn't correspond to any value in the enum...

We should be protected by the type system against unmatched Int's in the map as long as you have sane Enum instances.

One would hope so.

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... but you don't get an exception if you try to pass in, say, a large Integer. Prelude> fromEnum (2^32) 0

In essence, you're using Enum as a hash function, but not making any provision for hash collisions.

Unless I'm mistaken, the Enum typeclass _is_ a hash function who's keyspace is the range of Int that doesn't make any provisions for collisions.

Hash functions traditionally map integers to integers, so I would describe fromEnum as "like" a hash function, but that's not important.

And yes, hash functions collide, which is why hash tables employ various methods for distinguishing keys that hash to the same values. EnumMap silently passes this responsibility to the user, without even a note in the documentation.

-- Dave Menendez http://www.eyrie.org/~zednenem/