Re: Containers - nontrivial element access

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Maciej Sobczak <see.my.homepage@gmail.com> writes:

> On 3 Pa , 00:20, Matthew Heaney <mhea...@on2.com> wrote:
>
>> > BTW - above, PX plays the role of that additional variable that is
>> > sneaked around to the second procedure. Here it just pretends to not
>> > exist by taking the form of a parameter in the outer procedure. I
>> > don't think there is a reasonable way to avoid it.
>>
>> The number of "additional variables" is exactly the same in both the C+
>> + and Ada examples.  The only difference is how the variables are
>> named.
>
> No. The difference is in whether the subprogram's protocol is fully
> described by its signature.
>
> Your nested procedures have the signature that gives provisions for
> one parameter only. The other one is sneaked in bypassing the
> signature (so that the protocol is wider than the signature and this
> is not explicit). This hinders analysis.

I don't agree.  In Ada, and many other languages, you have to get used
to nested subprograms, and the fact that they can see more-global
stuff.  It's really not a big deal, so long as you keep them small.

> I can even think about coding standards that explicitly forbid
> subprograms that use anything other than what is in their signature
> (except for the main subprogram, which might need to access some
> library-level objects).

I can imagine that, too.  In fact I've seen it.  But it's not really a
good idea.  You can't reasonably do iterators, for example, without some
sort of nested procedures.

> Your solution requires some dose of liberal thinking, which I'm not
> easily willing to accept in the language that boasts high-integrity
> mindset. ;-)

- Bob