Re: Is the Writing on the Wall for Ada?

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

Marin David Condic wrote:

 > Like I said, I've never personally used it for anything (and yes, I
 > do embedded work as well as other things) and I'm wondering if others
 > have actually used it in practice or do people just hop over to
 > Unbounded_String the instant the type String seems to be the wrong
 > answer.

I initially invented what is now Bounded_String when I needed to create 
a ragged array of names in Ada.  I posted it to the ARG list (so long 
ago it was actually the LMC list) in answer to someone saying "It would 
be nice to have the equivalent in Ada of PL/I's char(N) varying."

There are some tricky bits to writing the package in Ada and making it 
would "right" and efficiently.  You have to have two record types.   The 
inner record type has a discriminant that doesn't depend on the outer. 
And defining the "&" overloadings is tricky--put in one too many and 
nothing works.  But as it is you can write:

    package Bounded is new
                 Ada.Strings.Bounded_String.Generic_Bounded_String(30);
    use Bounded;

    Foo: Bounded_String := Null_Bounded_String;
    Bar: String := "ABCD";
  begin
    Foo := Foo & Bar;
    Put_Line(' ' & Foo);

So I never understand all those complaints about explicitly converting 
to and from Bounded_String (or Unbounded_String).

In any case, people kept remembering that I had some working solution to 
the problem of ragged arrays in Ada, and sending me e-mail to get a copy 
of the package.  I probably rewrote it from memory a half-dozen times 
because I wasn't answering mail from a system where I had a copy.  (The 
body of the package is trivial, the key part is in the private part of 
the spec.)

Since lots of language experts would remember that there was a solution, 
but would e-mail me becuase they didn't remember the 'trick', it got 
added to Ada 95. Unbounded_String was essentially an argument by example 
for supporting Adjust for non-limited controlled types in Ada 95.

-- 
                                      Robert I. Eachus

"Quality is the Buddha. Quality is scientific reality. Quality is the
goal of Art. It remains to work these concepts into a practical,
down-to-earth context, and for this there is nothing more practical or
down-to-earth than what I have been talking about all along...the repair
of an old motorcycle."  -- from Zen and the Art of Motorcycle
Maintenance by Robert Pirsig