Re: 'with'ing and 'use'ing

[Robert A Duff <bobduff@world.std.com>]

rh@signal.dera.gov.uk (Roger Hoyle) writes:

> 1) Is this basically a good idea? It seems sensible to me, but then I know
>    little about Ada. (I'm asking about generally not 'use'ing stuff, not
>    specifically my current situation)

You've just started a language war between the two dialects of Ada --
the use-phobes and the use-philes.  ;-)

And then there's the folks who advocate renaming all packages as
incomprehensible abbreviations, so you can say XQYBC.Grind_Upon_List.  ;-)

I slightly prefer using use clauses.

Of course, you don't have much choice -- the existing code doesn't use
use, so presumably the names were chosen with that in mind.

>    the operators (=,/=,>=,<=) etc for some of the types in the main
>    package. The only way I seem to be able to get access to these operators
>    is to 'use' the package. Is this right, or am I missing somehting?

This is a trick used in Ada 83 to avoid use-visibility for identifiers,
but still allow the operators to be directly visible.  (While saying
``Foo.Bar(X, Y)'' might be reasonable, saying ``Foo."+"(X, Y)'' is an
abomination.)  Yes, you need to say "use Whatever.Ops;" for this trick
to work.  The trick is no longer needed in Ada 95 -- use "use type"
instead.

The trick is a little bit dangerous, because the code in the Ops package
is so boring that the reader assumes it says the obvious, without
reading it carefully.  I remember spending some time tracking down a bug
caused by saying something like ``function "xor"(...) renames "and";''
-- a cut-and-paste error.

- Bob