RE: Hash functions

2003-08-20 Thread Simon Marlow
 
 Many thanks for Data.HashTable, which I am about to use.  
 Unfortunately
 I seem to need an unseemly hack because the key I want, 
 namely ThreadId's,
 don't have a hash function defined, and defining one requires 
 me to muck
 around with GHC internal functions.  Could some more hash functions be
 provided?
 
 The logical method would be to have
 
 class HashKey key where
hash :: key - Int32
 
 and define it for as many types as possible.

I think the reason I didn't do this was because the choice of a hash
function usually depends on more than just the type of the data you want
to hash.  For example, there are lots of hash functions over Int, but
you'll want to pick one that works well for the distribution of values
you have.

There really ought to be a way to get an Int from a ThreadId, though.

Cheers,
Simon
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Hash functions

2003-08-19 Thread George Russell
Many thanks for Data.HashTable, which I am about to use.  Unfortunately
I seem to need an unseemly hack because the key I want, namely ThreadId's,
don't have a hash function defined, and defining one requires me to muck
around with GHC internal functions.  Could some more hash functions be
provided?
The logical method would be to have

   class HashKey key where
  hash :: key - Int32
and define it for as many types as possible.

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