Re: A simple ADA puzzle (I haven't the answer)

[Hyman Rosen <hyrosen@mail.com>]

Dmitry A. Kazakov wrote:
> What's the gain of limiting scope here? A relief for lazy
> programmers, who do not want to create extra *.h files?

The same gain as any limitation of scope - localizing things
to the narrowest region where they are needed. It is no less
sensible than Ada's declare statement. I often write tiny
classes whose job is nothing more than invoking a cleanup
function on an object in its destructor. I put them right next
to the object they will be handling.

> Limiting scope is useful, but it should be made consistently.
 > Clearly a nested thing should see everything from its scope.

C and C++ do not choose to allow closures because of difficulties
with function pointers that result. So it is clear that access to
local variables will never be permitted. The question is then
whether to also forbid a useful thing because of misguided efforts
to impose a useless philosophy. Fortunately the answer was "no".

> Talking about uneducated programmers how would you explain one of them
> what and when will be visible? Ada's choice was to give a clear,
> though unpleasant answer, rather than vague "yes, but".

As I have said, it's extremely simple. Automatic variables are invisible.