[pro] "fhash"

[Marco Antoniotti]

On Jun 13, 2011, at 21:18 , Daniel Weinreb wrote:

> Friends,
> 
> I wrote a little package for "fash hash tables", which provide an
> abstraction that is analogous to that of Common Lisp hash tables, but
> is faster for tables with few elements, and only slightly inferior for
> tables with many elements.
> 
> I did this because performance analysis showed that our system was
> spending too much time in hash table operations, and using the new
> package helped.
> 
> I have recently been cleaning this up, one reason being that I'd like
> to open source it.  The function names used to be things like getfhash
> and mapfhash.  Now they are like fhash:get and fhash:map-elements and
> so on.
> 
> However, before I open-source it, I was to make sure it's "right".  It
> recently occurred to me that the package name "fhash" has problems.
> 
> Here are pros and cons of changing it that I can see.
> 
> Pro: I's not a hash table in the small-cardinality case; it's a linear
> lookup.  So the name is not actually accurate.
> 
> Pro: Calling such a data structure a "hash table", even as Common Lisp
> does, is an abstraction violation.  Whether it works by hashing is an
> implementation detail.  The Java collection library calls this a Map.
> Python calls it a dictionary.  Clojure calls it a map.  Those are both
> better names.

Actually, in Java the naming reflects the separation between abstraction and implementation.  AFAIU, clojure does not quite do this and neither does Python.

I would advocate settling down on a Java-esque nomenclature with MAP or DICTIONARY as "names" for the abstraction and with different names for the implementations; e.g.,  DICTIONARY-TREE, DICTIONARY-FHASH, DICTIONARY-HASH-TABLE, you name it....

Cheers
--
MA




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Marco Antoniotti, Associate Professor				tel.	+39 - 02 64 48 79 01
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