Why are functors better? (Re: [Caml-list] Map efficiency?)

["Yaron M. Minsky" <yminsky@cs.cornell.edu>]

On Fri, 2003-11-07 at 03:27, Jean-Christophe Filliatre wrote:
> [ Some discussion of methods for building maps without functors ]
>
> (But the functorial interface is definitely the best, of course.)

I don't understand this perspective at all.  Functors seem like a fairly
problematic corner of the language.  In this case, except for some
possible efficiency issues, it seems clear that a non-functorial map is
preferable, for simplicity and ease-of-use issues, and performance
aside, I can't see much to recommend the current functorial approach.

Functors would be a lot more useful if they could be used as a
large-scale structural tool.  Sadly, the current implementation makes
this quite difficult, since there's no good way of parameterizing
multiple modules at once (as noted in a previous thread.  See

http://groups.google.com/groups?q=group%3Afa.caml+functors+yminsky&ie=UTF-8&oe=UTF-8&hl=en&btnG=Google+Search

for details.)  For most situations where you'd really need them, they're
not powerful enough.  And for the situations where they're powerful
enough, they're usually overkill.  Map and Set are examples where they
almost strictly get in the way.

y

-- 
|--------/            Yaron M. Minsky              \--------|
|--------\ http://www.cs.cornell.edu/home/yminsky/ /--------|

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