Re: Other Ada Standards (was Re: SIGada Conference)

["Robert I. Eachus" <rieachus@comcast.net>]

Nick Roberts wrote:

> Context clauses must be one of the most frequently used constructs in Ada.
> I think they deserve attention for that reason.

First, I'd like to point out that Bob Duff and I are relatively close in 
our positions on this.  The only issue with adding "with and use" in 
Ada0Y is whether it is worth the cost--and that is a close call.

With implies use can be made to work.  But I think the gymnastics 
required make it a non-starter.  Bob is willing to consider it. ;-)

But I think the relative cost of any with implies use variation is too 
high to make it into this revision.  Adding "with and use" to current 
context clauses should just be a bit of syntactic sugar for most compilers.

Anyone who argues that "with and use" is eight characters longer than 
"use" needs a better text editor.

> I suggest that 'with and use A.B.C;' is used, and means /exactly/ the same
> as 'with A.B.C; use A.B.C;' (it fails if 'with A.B.C;' fails). It's too
> confusing for 'use A.B.C;' to imply 'with A.B;'. I fear a reviewer could be
> sent into a spin searching for a library unit named 'A.B.C'.

I agree.  From the point of view of a reader, "with and use" is a slam 
dunk compared to use implies with.

> I also like the idea of 'with X renames A.B.C;' a lot. I would love to be
> able to write, for example:
> 
>    with ASB renames Ada.Strings.Bounded;
>    procedure ... is
>       ...
>       package My_Strings is new ASB.Generic_Bounded_Length(100);

Interesting idea.  I like it, but I would have to see what it looks like 
fleshed out.  Is the name Ada.Strings.Bounded also visible?  Can I say:

with and use ASB renames Ada.Strings.Bounded; --?

Incidently, you can currently write:

with Ada.Strings.Bounded
package ASB renames Ada.String.Bounded;

in your environment and be done with it.

-- 
                                           Robert I. Eachus

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