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Subject: Re: Ada Popularity: Comparison of Ada/Charles with C++ STL (and Perl)
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From: Matthew Heaney <matthewjheaney@earthlink.net>
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Date: Mon, 04 Oct 2004 12:16:58 GMT
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> It is because they are not arrays. But why an ordered list should not
> implement an array interface? In my view it should, making the above
> legal for lists.

Stop obsessing about syntax.  If you want a consistent interface for
containers, you have that in AI-302 (but of course it's not an "array"
interface):

procedure Op (Container : <container's type>) is
   C : Cursor := First (Container);
begin
   while Has_Element (C) loop
      Process (C);  --or Process (Element (C))
      Next (C);
   end loop;
end Op;

Actually, if you intend on iterating over all the elements in a
container, the passive iterator is preferred:

procedure Op (Container : <containers's type> is
begin
   Container.Iterate (Process'Access);
end;

If you have an array type, then you can give it a container-like
interface for the purpose of binding an array object to a generic
algorithm.  I showed how to do this in an earlier post.
   


> I do! I hate implicit iterators, I prefer loops where
> possible. Especially, because exit conditions, nested iterations,
> exception handling become visible.

If you intend on traversing every element in the container, then use a
passive iterator.  It's more efficient, and less error-prone.

If you have exit conditions, then go ahead and use an active-iterator
style loop.


> [ Ranting: 40 years spent in developing readable, safe, well-structured
> language constructs, only to replace them with nested function calls a la
> Lisp? ]

This is a specious comparison.