Re: Negative Logic (was: Re: an infinate loop)

[dewar@gnat.com (Robert Dewar)]

Jeffrey Carter <jrcarter@acm.org> wrote in message news:<3B50706F.D24FB0ED@acm.org>...
> The material on loops other than FOR loops is heavily revised in this
> edition, to present general loops before WHILE loops. This reflects 
> the observation that beginners deal more naturally with "positive 
> logic" stating a positive condition to exit a loop ...


Note that I agree that *other things being equal* conditions which
have a NOT are more complicated to understand than those that don't
(any extra operator adds complexity, other things being equal).

The trouble is that things are typically NOT equal, and what worries
me about a rule like this is it will cause people to recast their
conditions, using Demorgan's laws or whatever, to desparately avoid
a NOT, resulting in something more complex.

Sort of like the situation where convoluted boolean flags are added
in a desparate attempt to avoid a goto that would be the most natural
way of writing the code, e.g. to reflect a loop continue statement in
a language (like Ada :-) with no continue statement in loops.

Of course AQ&S is just intended to be guidelines anyway, but I far
too often see people turning these AQ&S guidelines into rules :-(