[Caml-list] Discarding elements from a list

[oliver@first.in-berlin.de (Oliver Bandel)]

Hello,


after Remi has pushed my towards rewriting my
"I do it like I know it, and therefore imperative"
version of a program into a functional version of
this program (thanks, Remi, I have explored a lot
new things since then :)) I sometimes come to
this problem:

I have to use a partial list.

In the reference manual I did not found any
stdlib-function, and so I have two ideas,
of how to perform e.g. a list, which is used
without the head (throwing away first element):

a) Converting the list to an array, shorten the array,
   converting back to a list, using the list in a functional
   manner.

b) Using pattern match to throw away the first element, then
   working in the part after the "->" with a function, which
   works on the rest of the list.

c) using a function, which uses an index, for counting, at which
   position we are inside of the list


This problem arises, when a list, on which should be worked,
will be created and it must be used a part of it (e.g. all
elements but the last or all elements but the first), like
creating a multiplication of the last and the current element...
(like fibonacci uses addition, I need multiplication here)
and when the first or last is necessary for some calculation,
but should be thrown away for some other calculation.

Because I have no criteria to decide, which solution I should
prefer (and why), I always rethink the problem again,
and the decision-process slows down.

So, why should I use which solution?

(And how to select parts of a list in general, not only
 throwing away the first or last element?)

Any hints?


Ciao,
   oliver
-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners