Re: [Caml-list] Large projects in OCaml

[Jon Harrop <jdh30@cam.ac.uk>]

I have been using ocaml to write a vector graphics library over the past four 
months. I intend to commercialise it. However, I am not yet sure exactly how 
I can do that...

From my experiences, I would say that you are likely to find programming in 
ocaml to be vastly more productive than programming in C++. In the case of my 
project, for example, I would say that development in ocaml is about 10 times 
faster than in C++ and code density is about 4 times greater. I would also 
say that your programming style (if you are used to imperative style) is 
likely to change significantly over the first month of using ocaml. It may be 
worth noting that I had already dabbled in functional programming as an 
undergrad.

I think it is important to emphasise that the efficiency of developing in 
ocaml goes a long way to offsetting the (relatively minor) drop in 
performance. This is because a given project has a finite lifetime and, in 
that lifetime, you can try a much wider variety of approaches and algorithms 
using ocaml than you could in C++.

If you want to see examples of good ocaml code to learn from then I'd 
recommend looking at the core library (in the ocaml distribution) and a 
select few third party libraries. However, you are unlikely to appreciate the 
way in which the code is written without some more intricate knowledge of the 
language itself.

> a) Are there examples of
> commercial s/w developed in OCaml?

I am not aware of any existing commercial software written in ocaml.

> b) Is the native compiler/runtime/tools mature for
> large commercial projects?

Primarily due to the clean design of the language itself (I believe) the tools 
are already of extremely high quality. I have found several bugs in gcc but 
none in the ocaml compilers, for example. Having said that, I pushed gcc to 
its limits (e.g. gratuitous template partial specialisation) but I have never 
used the more risque features in ocaml.

However, if you are planning on using external libraries in other languages 
then, I think, it is highly likely that you will need to develop your own 
interfaces to them (which you could then productively distribute for free!). 
This is mildly tricky as (I would say) there is relatively little 
documentation and it involves the use of several magic C macros. You could 
also try some of the automated tools (SOAP, camlidl).

> We would really appreciate feedback from folks who
> have worked on large projects with OCaml. If this
> has been answered earlier, we appreciate pointers
> to the thread(s).

There are some other, important aspects which you haven't covered:

The type-safe linking offered by ocaml makes for a very brittle interface 
between objects (see Xavier Leroy's post to this list on 17 May 2004 entitled 
"Ocaml shared libraries"). Therefore, I don't believe it is feasible to 
distribute commercial code in object form. If you intend to sell your code to 
programmers and you don't want them to have your source (like me!) then 
you're a bit stuck. I suspect that selling executables for the end-user would 
be comparatively trouble-free.

There are some issues with libraries too. The compiler comes with a "core" 
library which the compiler itself uses. Although these are extremely well 
written, they can be a little quirky and their functionality is quite limited 
(e.g. data structures). Although there are other libraries, such as Extlib 
and "the library formerly known as Extlib":

http://sourceforge.net/projects/ocaml-lib
http://raevnos.pennmush.org/code/annexlib/index.html

for example, there is no "Standard library". Part of this problem stems from 
the fact that, the INRIA team is intended for research and not for the 
development of such (mundane) code and although they may recieve great code 
snippets for contribution to the "core" library, they cannot accept them due 
to copyright issues:

http://caml.inria.fr/archives/200403/msg00171.html

Additionally, people who know about external libraries often aren't very good 
at designing/writing ocaml code and vice-versa.

Finally, I am not sure how well ocaml runs under Windows.

HTH.

Cheers,
Jon.

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