[pro] "fhash"

[Daniel Weinreb]

Thank you for letting me know about this.

One of the things I feel strongly about, though, is avoiding names like
dictionary-get.  Fhash's package is the kind where you're not supposed to do
a "use".  You're supposed to get at the external symbols by using explicit
package prefixes, so the dictionary- isn't there.

Anyway, I'll take a look at what you wrote.  Thanks again.

-- Dan

On Mon, Jun 13, 2011 at 9:52 PM, Pascal J. Bourguignon <
pjb at informatimago.com> wrote:

> Daniel Weinreb <dlw at google.com> writes:
>
> > 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.
> >
> > Con: Common Lisp already uses the name "hash table", so it would be
> > easier for existing Common Lisp programmers to see the analogy.
> >
> > Advice?  Thanks!
>
> Cesarum has an ADAPTATIVE-DICTIONARY abstraction that does that:
>
>
> https://gitorious.org/com-informatimago/com-informatimago/blobs/master/common-lisp/cesarum/dictionary.lisp
>
> It uses hash-tables when it's fast, and faster data structure when
> hash-tables are slow (ie. when they don't have enough elements).
>
>
> --
> __Pascal Bourguignon__                     http://www.informatimago.com/
> A bad day in () is better than a good day in {}.
>
>
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