Re: [Ocaml-lib-devel] Xarray : resizeable arrays (first cut)

[Blair Z. <bl...@or...>]

Hideo Bannai wrote:
> 
> Hello list,
> 
> At Sun, 13 Apr 2003 19:04:17 -0700,
> Blair Zajac wrote:
> >
> > Nicolas Cannasse wrote:
> > >
> > > If (-1) make some sense, I'm not so sure about (-2) and (-3) :-)
> > > So I would prefer an explicit get_last x that is perhaps less confusing to
> > > code readers.
> >
> > I have no problem with the -1, -2, -3, etc usage and find is very
> > understandable.  I haven't heard any complaints from Perl users on
> > this usage.
> 
> I can imagine why Perl users wouldn't complain about this, but as
> an OCaml user, I think I will :-). I can see that there would be no
> problem if the index is written explicitly as -1, -2, -3, etc.
> However, I don't like the idea because it essentially overrides
> (to some extent) the very useful array bounds checking that OCaml
> provides, and could `hide' bugs when variables are used as the index.
> 
> Maybe it's just me, but I often (er, at least sometimes?) find myself
> writing code like:
> 
>         let index = x - y + i in
>            do something with (Array.get array index)
> 
> where x, y and i move around in a complex way, and the problem
> is that I sometimes forget to do +1 somewhere, and end up getting a
> negative value as index (but is found easily since it raises
> an exception!).
> 
> So I would very much like to have the function which doesn't allow
> negative indices to be kept (preferably leaving the name as [get], so
> as not to confuse users of standard arrays). If we must have a [get] with
> negative indices, it should be a different function.
> 
> What do you think?

Sure.  I don't feel strongly about this one.  Let's have a separate
function for indexing from the end.

Best,
Blair

-- 
Blair Zajac <bl...@or...>
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