Re: [Ocaml-lib-devel] Proposal for new list functions

[Brian H. <bh...@sp...>]

On Wed, 10 Aug 2005, skaller wrote:

> On Wed, 2005-08-10 at 00:28 +0900, Janne Hellsten wrote:
>
>> First one is called fold_left_while.  It works the same way as
>> fold_left except that it breaks the loop as soon as a "while
>> predicate" returns false.
>
> Sounds good, but must not be implemented as you
> have written it. The real implementation must use an
> inner exception to stop recursing, we do not want
> to uselessly scan the rest of the list after the
> termination condition is found.

I don't think we need an exception to do this.  Wouldn't this do:

let fold_left_while f p init lst =
     let rec loop accu = function
         | h :: t ->
             if p h then loop (f accu h) t else accu
         | [] -> accu
     in
     loop init lst
;;

>> The second function is called split.
>
> List.split already exists, it splits a list of pairs
> into two lists, perhaps call it "part"? (short for
> partition .. but that isn't quite accurate).

List.partition already exists as well.

Brian