Re: PL/SQL -> Ada

[Tucker Taft <stt@averstar.com>]

"Marin D. Condic" wrote:
> Well, I'm thinking of situations where I know *exactly* how many bytes
> are occupied by specific items and I have to line those bytes up with
> data coming from the outside world, so I can't accept alternative
> representations and I can prove beyond any shadow of doubt that the
> bytes will in fact fit just like I said they would and for various
> language and/or implementation reasons the compiler says "Sorry, Chalie!
> No can do." My problem isn't a misconception about the language or its
> implementation. My problem is getting what I want out of the compiler.

As a user I can sympathize.  As a compiler builder, I will
say that supporting representation clauses in their full
generality is an enormous pain.  I frequently look longingly
at languages which provide little or no control over representation,
and wish I could be so lucky.  

To give you an analogy which might make you feel sorry for us
poor compiler-writer slobs.  Imagine a chauffeur and a passenger.
The compiler is the chauffeur, and the programmer is the passenger.
When there are no representation clauses, you get to tell the
chauffeur to drive the car to the store, and that is about it.
When there are representation clauses, you get to tell the chauffeur
that you want them to put their left foot exactly there, their right
foot there, their left index finger here, their right thumb there,
and their left pinkie over here.  *Now* drive to the store, at exactly
the speed I tell you to, with your tires following exactly along the
pair of white lines I drew on the road earlier today.

In the original scenario, the chauffeur really only needs to know one
way to drive, and they can handle all the road hazards that come up
in the way they choose.  In the second scenario, the passenger is
exerting so much control, that the chauffeur must learn a hundred
different ways to drive, in millions of different combinations, so
they can follow exactly the orders being given by the passenger.

Anyway, so much for the compiler writer's soap opera...

> MDC
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>     --  Willie Sutton when asked why he robbed banks.
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-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA