Re: Side-Effects in Functions [Rosen Trick]

["Nick Roberts" <nickroberts@adaos.worldonline.co.uk>]

Just briefly, because I don't want to waste any more of my time on this, I'm
not entirely sure whether Robert is being serious, or is just arguing for
the fun of it (or something).

As to the issue of whether Ada should permit in-out parameters in functions,
I hold no strong opinion, and my original point had nothing to do with this.
Maybe it would be a nice idea, but you can always use a procedure instead;
no big deal. The 'problems' cited by various people about using access
parameters for interfacing with C functions are silly: if you need to be
able to pass a null value, you use an access type (and pass it in as an 'in'
parameter); again, no big deal.

On whether it is good practice to program functions with side-effects, in a
procedural language which doesn't specify the order in which the arguments
of functions are evaluated (such as Ada), I hold the very strong opinion
that it is generally not, for the perfectly rational, and well-established,
reason that it can introduce subtle and pernicious bugs. Robert has said
absolutely nothing to refute this. Twisting the argument between what can
and should be done may be a clever rhetorical technique, but it isn't good
science.

--
Nick Roberts