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From: "Nick Williams" <nickw@acm.org>
Newsgroups: comp.lang.ada
Subject: Re: A case where Ada defaults to unsafe?
Date: Thu, 3 Jan 2002 23:38:45 +0000 (UTC)
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Date: 2002-01-03T23:38:45+00:00
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"Hyman Rosen" <hyrosen@mail.com> wrote in message
news:3C34E43E.5070906@mail.com...

> >>But get away from C/C++ for a moment. In pure Ada terms, isn't it less
safe
> >>for the defaults to be "and" and "or" instead of "and then" and "or
else"?

> > Perhaps for ex-C programmers it is. But that's certianly not the only
pitfall in
> > the language for ex-C programmers.

> > If you were instead brought up to believe that boolean "and" is
communitive,
> > like they teach in math/logic classes, then it makes perfect sense. In
that
> > case, "and then" is just a nice shorthand for " then if ... then".

> You haven't answered my question, though. Isn't the commutative semantic
> less safe than the short circuit one?

It's 'unsafe' to the extent that someone who is badly informed, or who
expects Ada to behave the same way as C, might use it unsafely: you might as
well say signed integer types are unsafe. You ask the question in 'pure Ada
terms', but in 'pure Ada terms' they're just as safe as each other: a 'pure
Ada' programmer would have no baggage in terms of preconceived expectation
of short-circuiting behaviour from boolean operators.

Cheers,

Nick.