Re: Ada functions versus arrays (i.e. () vs [] )

[mph@lion.inmos.co.uk (Mike Harrison)]

In article <608@software.software.org> blakemor@software.org (Alex Blakemore) writes:

>I agree that side effects are best avoided - they definitely mess up this
>scheme.  I assume the language designers left them in for the 
>very few times when they are justifiable (e.g. next_random_number).
>Quite possibly a language design error forced on them by C programmers :-)
>
Remember that preliminary Ada had procedures, functions *and* 'value-returning
procedures'. 
Functions were not allowed to have side-effects, value-returning procedures
were.

It's all a long time ago but, I talked to several members of the design team 
about this, and if my memory is correct, the problem was that detecting
side-effects in non-trivial functions (written in an imperative langauge) was
impracticable (if not impossible).
So they decided not to include in the language concepts which could not be 
enforced.
The same argument (about side-effects) also led to the removal of the ASSERT
statement.

Mike,


Michael P. Harrison - Software Group - Inmos Ltd. UK.
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