Jon Harrop wrote:

>> On Saturday 22 October 2005 02:04, Stephen Brackin wrote:
>>
>
>>>>My biggest initial question is why OCaml has both a modules system and
>>>>objects: Aren't they different ways of accomplishing the same things?
>
>>
>> Both modules and objects allow you to encapsulate related
definitions, yes.
>>
>> However, modules are much more static by nature and objects are much
more
>> dynamic, i.e. you get stronger static checking using modules than you do
>> using objects, giving more comprehensible error messages and more
robust and
>> faster code.


That's certainly true ... I've probably spent twice as much time
debugging type errors in mutually recursive objects as I have on all
other kinds of errors put together.

On the other hand (as Jon's statement implies), it's much easier to
write extensible code with objects. When you call a function on a module
(except within a functor) you are using a specific implementation,
whereas you can call an object method, say foo#display (), where foo can
be any object with a 'display' method that matches the expected type.

And even if modules and objects were functionally equivalent, I think
one of the great things about OCaml is the freedom it gives you to
structure your application in the best way for the problem.

--
Matt Gushee
Englewood, CO, USA