Re: Lack of formal syntax undermines Ada

[Adam Beneschan <adam@irvine.com>]

On Apr 11, 3:37 pm, John McCabe <j...@nospam.assen.demon.co.uk.nospam>
wrote:
> Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
>
> >John McCabe <j...@nospam.assen.demon.co.uk.nospam> writes:
>
> >> As I understand it, that was deliberate; Ada's feature that functions
> >> may not have side-effects ...
>
> >Ada functions can have side effects.
>
> Bugger - where did I get that idea from then (have to admit, it's been
> a while since I paid a lot of attention to Ada!)

There was an early, pre-1983, version of Ada that had a rule that
functions couldn't have side effects; this version also had "value-
returning procedures" for those cases where you really needed
something that could have side effects with the syntax of a function.
(I think value-returning procedures were allowed to have what are now
referred to as OUT and IN OUT parameters, but I'm not sure.)  Since I
don't remember a rule that functions weren't allowed to call
procedures, I don't know how they expected the side-effect rule to be
enforced; maybe the authors figured they could just decree it to be so
and stick implementors with the burden of figuring out how.
Thankfully, that got dropped before the language became a standard.

This was a long time ago, so of course my memory is hazy.  I haven't
looked to see if this draft version of Ada exists somewhere on the
Internet.

                                -- Adam