Re: Additions to extlib

On Mon, Jun 28, 2004 at 03:33:56PM +0300, Jere Sanisalo wrote:
> Hi,
> 
> just a few thoughts on adding new modules to extlib. One useful feature
> would be a module that offers different kinds of iterators on number ranges.
> I've found myself writing some nasty for loops and I've been thinking that
> wouldn't it be useful is there was something like List.iter for a number
> range. Attached is a blanket base where to build more iterators (like
> floating point iterators with a given step or multidimenstional iterators).

I like the iterators.

One gripe I have about them (and indeed about the List.iter and
List.map functions built into the library) is that the parameter order
is just plain wrong!  It's much clearer to write:

List.iter list (fun elem ->
                  very long function definition
                  ...)

instead of:

List.iter (fun elem ->
             very long function definition
             ...) list

Because what you're iterating over ('list') gets lost in the second
version.

Why can't we also iterate over floats?  I consider it a problem in
OCaml that there is no for ... construct for floats.

> Also coming from a C++ background, I've found the lack of a scope finalizera
> bit disappointing. It would be nice to have a function such as this in
> extlib:

Normally this function is called 'finally'.  Is this function already
in ExtLib?  A quick grep over my version shows that it is not.  There
is a rather convoluted version of finally defined at the end of this
file:

http://www.fungible.com/stream_fixed.ml

Of course what would be really great (and probably not possible) would
be to have a way to run a finalizer when a variable goes out of scope.
This would allow us to create, eg., file descriptor objects which
automatically close the underlying file descriptor at the earliest
opportunity.

Rich.

-- 
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