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OCaml troll on Slashdot
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Date: 2005-03-16 (10:25)
From: Oliver Bandel <oliver@f...>
Subject: Re: [Caml-list] OCaml troll on Slashdot
On Wed, Mar 16, 2005 at 02:05:43AM +0100, Yoann Padioleau wrote:
> Oliver Bandel <oliver@first.in-berlin.de> writes:
> > But with
> > 
> >   let columnSize = 5;;
> >   and with
> >   let numRows = 7;;
> > 
> > (look at the ";;" it seems he had used it in the toplevel... :))
> And ? 

Only nice to see.
Nothing more. ;-)

It's only that I think about it, because he
talks with seemingly bad intentions about OCaml.
(a kind of C++ dogmatism)

> First, I dont think it is a good idea to make fun of people who try to use caml.

I don't do that.

But I can't see that there is really an interest in exploring OCaml.
If he only would be cynic about "well I tried it, but it has proven
it's a crap language... but I give you (experienced OCaml programmers)
the chance to show me that it isn't bad (and *I* have o learn the language)"
then this woul be ok.

But it seems that he's saying: "well, OCaml never can compete with C++".

Maybe I'm wrong here and he's a good guy. But IMHO it seems he's looking
for proved Ocaml-failure (and not for "well, I tried it, it seems OCaml sucks,
but please tell me it does not!", which I could accept).

> Second, many people I know still put ";;" cos they were taught that way

Hey, that was the way I started too! :)

That comment from me only shows: Well, it seems he's an absolute beginner.

To be a beginner is not wrong. It's good!
To be a beginner every day and every time means: to be open for new
things every time!
That's good! :)

But as stated above: Would be nice if the OCaml-bashing would contain at least
a bit of "maybe I'm wrong, and I only use cynism, because I thaught it
performed better (or It's easier to learn).

Maybe I've overlooked that positive-thinking approach behind
his harsh words?!

>  (at the very beginning with caml-light I think you were forced to put those ";;", it
>   became optional later, and habits are hard to change for many people :) )
> Third, doing stuff at the toplevel is a good idea.


So, what are we talking about?

Do you think *I'm the bad guy*?!

"mea culpa" ?!!!????

> > which does not really looks tail recursive.
> > 
> > Called more than 2 * 10^6 times...
> > 
> > And many other examples...
> > 
> > 
> > e.g. this one:
> > 
> > (* applies a list of functions to an argument *)
> > let rec applyFunctionList functions argument =
> >   (* 267386 *) match functions with
> >         | [] -> (* 9782 *) []
> >         | f::rest -> (* 257604 *) (f argument)::(applyFunctionList rest argument);; 
> > 
> > "only" called 267386 times, but when looking how the arguments
> > are used:  also applyFunctionList is not tail recursive...
> > ...and even if called less than 10^6 times... it's a function that
> > creates a list in a non-tailrec way.
> > 
> > IMHO this is the reason, why the program performs so badly!
> IMHO the reason it was slow is because it used associative list (instead of Map) 
> for associative access,

Maybe it is.
I don't say it is *not*.

I have not loked into the code in so much detail
that I could see that the associative map is the problem
or is not.
If the list is short, an associative list may not perform so badly.
(Correct me, if I'm wrong.)

But IMHO creating the environment for a function that is non tail-rec
needs more ressources than using assoc-lists ionstead of maps
in that application (Correct me, if I'm wrong).

(And maybe - if it is always the case - that all depends on
the amount of data/how often functions are called and so on.

> and list of list (instead of array) for storing the grid.

Yes, that also seems to be a problem.

> I am not sure that making the function tail-recursive would have been the big
> hit in this example.

But as long as nobody tried it / analzed it, your assumption is
only an assumption, as my assumption is only an assumotion too!

... IMHO it makes sense in a field where THE solution is not
already known, to come out with ideas that are *possibly*
solutions to a problem.

So, nothing else is "use map instead of..."  and "use arrays instead of...".

The real freaks doesn't post to that thread, as it maybe is trivial to them,
to talk about that stuff...?!

> I often transform my functions to make them tail-recursive because of stack overflow pb, not
> that much because of speed pbs
> (and many functions in the standard library are not tail-recursive, such as map)

Well, maybe I have overestimated the tailrec-point,
but as long as there is not a proven counter-example,
the opposite of what I stated seems to be only an assumption too.

Maybe such freaks like the OCaml core-team, or M.Mottl will
see in milliseconds what is going on... but the whole thread
on slashdot (and here) seems to be guessing from many people.

If I'm wrong, please show me.

!!! To see different results it would be nice to have different implementations
!!! to compare them all!

> > 
> > Ths stuff of tail recursion - even if it took a while
> > until I got it - was one of the first things on this list,
> > that people told me that it is necessary....
> I am not sure it is the first optimisation trick to give to a fresh ocaml programmer.

That is a thing what special studied computer science people 
gave me as one of the first hints on that list.
(And wehen looking in SICP, it seems, that it's very necessary to think
abot it in more detail.)

Would be interesting to have different variations of the
code, using different ways of coding some special tasks
in different ways.... and maybe oe implementation,
that uses *all* suggestions.

To do it in the language shootout, as on Jon stated it, seems
to be a veryg good idea.

> This tail-recursion stuff is one of the thing I hate the most with fp because it forces
> you to change your code to adapt to the machine whereas it should be the 
> inverse.

But only because you hate it does not mean that changing the code will not result
in better performance.

At least for that list-creating stuff I have (e.g. reading in a file
and write it to a list of lines) I have seen the advantages (in speed!)
when using tailrec versions or imperative versions) instead of
simple recursion.

And some of that troll-code's functions are really doing that!
Build lists by building lists non-tailrec.

> I don't understand why the compiler don't do himself those transformations.

Well I understand, why a compile does not do that job: because it's
too complicate for a programmer of a compiler to implement that feature. ;-)

But on the other side I think the same: Why not implementing such stuff directly
into the compiler?! Would be nice...

(... or not, because we never would think about what we are doing then...)

> Why is it so hard to take a non-tail-recursive-function and make it a tail-recursive-one ?

It's not hard, it's only "practise, practise, practise" or
"exercise, exercise, exercise..." ;-)

One of the people on this list once shwed a way of how to change a loop
into tailrevc-stuff in general (shown for two or three args of a func).

(Remi Vacant?!).

Maybe I have somewhere a printed page of it and can look for it / find it...


P.S.: Well... too much beer this night... :(