Re: Association lists

[Marco Vezzoli <marco dot vezzoli at st dot com>]

nferrier@tapsellferrier.co.uk wrote:
> 
> >>> "Brian D. Carlstrom" <bdc@zurich.ai.mit.edu> 22-Jun-00 7:13:12 PM
> >>>
> 
> >Associative arrays are not hashtables, although they
> >have a similar API, because their performance is not
> >equivilent
> 
> I appreciate that.
> 
> But it's as near as dammit because an assoc-list is only an
> assoc-list whilst it has associaton pairs on it. It wouldn't be a
> problem (from the user's point of view) to optimize it into a
> hashtable within the compiler or interpreter.
> 
> This, it seems to me, would be the Scheme way - expressive and
> minimalist but with hidden, implementation driven,  power (a la
> loops).
> 

The scheme solution IMHO is 

hash table=vector of alists + hash function.

It has the same (theorical) performance of a java hash table and is
portable; slib has some implementations; however you have to manage the
gory details of rehashing in order to keep the load factor optimal.

Association lists are a good solution for almost-constant small
dictionaries and take advantage of the easy definition of literals in
scheme; when I need the full power of an hash table with kawa I use the
native java hashes (portability is not one of my concerns) and a small
api to convert alists into hash tables and vice versa.

I'm not sure that the behaviour of an 'intelligent list' is really easy
to define.

Marco

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Marco Vezzoli	marco.vezzoli@st.com
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