Re: Ideas for Ada 200X

["Robert I. Eachus" <rieachus@attbi.com>]

Russ wrote:

> Your suggestion would require some sort of advanced artificial
> intelligence to be built in to the compiler. The AI system would need
> to perform a very complex analysis of the overloaded "+" operator and
> decide how to deal with it.

Been there, done that, got the coffee mug.  Or didn't you realize that 
the current overload resolution algorithm essentially required for Ada 
compilers to pass the ACATS tests does just that?

>                         The only other alternative would be to
> have the "+" operator automatically defined for arrays. Either
> approach would constitute a major change in philosophy for Ada.

Hmmm.  Predefined operators for two dimensional arrays would be a 
change.  I don't think I'd consider it a major change.  As for one 
dimensional arrays, catenation is defined for all such types, and the 
boolean operations "and", "or", and "not" are predefined for arrays of 
Boolean, or arrays of any type derived from Boolean.  Adding predefined 
"+", "-", "*", "/", "mod", "rem", and "abs" wouldn't be much of a change 
at all.  I don't think it will happen, since the current choices are 
well thought out--but if there was a reason to change things, I'm sure 
it would happen.

The reason that the boolean operations are predefined for arrays is that 
it would be very difficult for a compiler to figure out the 
optimizations to use bit-wise operations on words otherwise.  If the 
same sort of problem was found with using the SSE and SSE2 instructions 
on arrays of small integers, I'm sure the language would change....

Catenation on the other hand, is just too important an abstraction for 
one-dimensional arrays to leave out.  For two dimensional arrays, it is 
a very uncommon operation.