[Haskell-cafe] Rethinking OO idioms

[John Goerzen]

On Thursday 30 September 2004 07:54 am, Jeremy Jones wrote:
> John (and Haskell community),
>
> I just subscribed to the Haskell mailing list the other day and this
> posting grabbed my attention.  I've been workin with Python for a few
> years now and have recently decided to try to expand my horizons to
> Haskell (and OCaml).  I love Python, but I feel like I could learn a
> lot that could be applied to Python from understanding FP languages
> like Haskell (and OCaml).  That being said, can you point me to any

One of the interesting things about Python is that it has slowly been 
adding functional programming mechanisms to the language.  Some of the 
constructs we all love in FP are available on Python.  For instance:

 * anonymous functions ("lambda" keyword)

 * nested scopes and the ability to return functions

 * iterable objects

On the other hand, Python's typing system is nowhere near as powerful as 
that of Haskell or OCaml.  OCaml, and to an even larger extent, 
Haskell, have a wonderful typing system: it's strong, yet it 
inobtrusive.  I am a fan of that, and it helps these languages scale to 
large projects better than Python -- while at the same time keeping 
them suitable for small ones (unlike, say, Java)

OCaml has an object system.  It's not as powerful as Python's in most 
respects, and can be loosely described as a functional hybrid of the 
Python and Java object systems <grin>

I find myself writing most of my new code in OCaml these days.  If I can 
manage to get a Haskell compiler built on AIX, I may move to 
Haskell :-)

(Building anything on that platform is difficult, sigh)

> documentation online or books that are more suited to a Python person
> trying to understand Haskell (and OCaml)?  Any help is appreciated.

This is a great resource:  Learning OCaml for C, C++, Perl, and Java 
programmers:

http://www.merjis.com/developers/ocaml_tutorial/

I wish something like that existed for Haskell.  I may write one 
someday. :-)

Once you know OCaml, though, Haskell will come a lot easier.  The typing 
systems are quite similar, as are many of the concepts.  I/O is very 
different though.  Haskell I/O is different from anything else I've 
ever seen, so I can't really come up with a good analogy for you 
there :-)

This is a good Haskell tutorial: http://www.isi.edu/~hdaume/htut/