Re: Introduction to Functional Programming in OCaml at Paris Diderot (MOOC)

I'm replying here to an older message, but what the hell.  Anyhow, the
course looks great.  I wish it started sooner than September 26th.  By
"Informatics" I'm assuming they mean "analysis of data" or the combination
of statistics and computer programming.  Or is there another definition for
Informatics?

I'm kind of proud of the following functions that I created while playing
around with the language.  I was wondering how I could reverse a list
without resorting to the @ operator.  Well I think I found a way to do it.

So....  ( Copied from memory, so forgive typos, mistakes, etc. )

*exception Empty_List of string ;;*

*(* Here I am borrowing the names of pre-defined functions in Haskell. *)*

*let rec last = function *
*                      |[ ] -> raise ( Empty_List "An empty list does not
have a last element!" )*
*                      |head :: tail -> if tail = [ ] then head else last
tail ;;*

*let rec init = function*
*                     |[ ] -> raise ( Empty_List "The init function only
applies to non-empty lists." )*
*                     |head :: tail -> if tail <> [ ] then head :: init
tail else [ ] ;;*

*let rec reverse = function *
*                             |[ ] -> [ ]*
*                             |lst -> ( last lst ) :: reverse ( init lst )
;;*

*I'm pretty happy with these functions, especially since the cons operator
or :: is supposed to be more efficient or faster than the append operator
or @.*

Of course I have to wonder why recursing over lists is better than
iterating over arrays.  In traditional imperative programming all these
things are done through iteration and array manipulation.  But in Ocaml and
Haskell these things are done by recursing over lists or linked lists
rather than arrays.  ( Although I realize that Ocaml does offer the array
data structure.  I'm not really sure if Haskell has arrays.  I don't know
that much about Haskell. )  So then this begs the questions: 1) Why is
recursion superior to iteration?, and 2) Why are lists better than arrays?
I know I'm playing the Devil's Advocate here, but it might be good to
reflect on why functional programming is the way to go rather than studying
a more "traditional" language such as C or C++ or Java.  I also recently
read some blog post where the author said something like, "We need mutable
data when modeling phenomena in the real world!"  He was casting some doubt
on the legitimacy of the practice of allowing only immutable data types in
a programming language.  He basically said that you have to assign,
reassign and update variables in order to successfully model real world
data.  Is that really true?  Any thoughts?  I appreciate the feedback.
Have a wonderful day.

Regards,

Douglas Lewit


On Sat, Jul 9, 2016 at 4:47 AM, Manfred Lotz [email protected]
[ocaml_beginners] <[email protected]> wrote:

>
>
> Hi all,
> I thought it is a good idea to call attention to a forthcoming OCaml
> beginner's course, starting at Sep 26, 2016 as an online course at FUN
> (https://www.fun-mooc.fr/).
>
> Introduction to Functional Programming in OCaml
> Université Paris Diderot, Sep 26 2016 till Dec 12, 2016.
>
> https://www.fun-mooc.fr/courses/parisdiderot/56002S02/session02/about
>
> Important for those, who like me do not (unfortunately) speak
> French, the course language is in English.
>
> I think it will at some point in time appear at the News section at
> https://ocaml.org/.
>
> --
> Manfred
> 
>