Re: Teaching new tricks to an old dog (C++ -->Ada)

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Jerry Coffin" <jcoffin@taeus.com> writes:

>...effort that's put into
> compile-time checks more or less directly translates into time and
> effort that was NOT put into better code generation and optimization.

True, but I think you misunderstood Peter Amey's point.  I believe he's
not talking about run-time checks that can be optimized away with some
compiler effort, but about purely compile time rules.  For example, both
languages have visibility rules, but I find Ada's visibility rules to be
less error prone than those of C++.

> Maybe...or maybe not. IME, absolute statements about generalities (e.g.
> all implementations of a language) are rarely accurate. Ada compilers
> vary quite widely, and I've certainly seen some emit code that included
> checks that were logically unnecessary. I'd guess that the current
> compilers are better, but perfection in this respect would surprise me.

It would surprise me, too, since it's provably impossible!
This is what Appel calls the full employment act for compiler
writers: no matter how smart a compiler is at optimizing,
you can always make it smarter.  And that's formally provable.

The real question is to what extent can checks be optimized away,
and how often one needs to resort to suppressing them, and this question
can only be answered via measurement.  By "measurement" I don't mean
bogus benchmarks written to make a point on one side or the other.  ;-)

By the way, *most* of the work a compiler does to optimize away checks
is the same as for other optimizations (despite what some Ada fans have
claimed in this thread), so optimizing away checks is not as costly as
you seem to think (in terms of compiler-writer's effort).

> Some areas are somewhat more questionable -- calling a class a "tagged
> record" is clearly a mistake, ...

Sorry, but if you think a class is called a tagged record in Ada,
you don't understand the language.

>... but it's open to question whether it
> should be classified under poor expression of the concept, or just
> general idiocy.

;-)

- Bob