Re: Enumerated "procedural" parameters

[rcd@nbires.UUCP (Dick Dunn)]

I think it's unfortunate that anyone ever suggested the idea of enumerating
procedures which might be called and suppying an enumeration value instead
of a procedural parameter.  The question [I hope!] was never whether one
could construct an Ada program which would have the same effect as a
program in another language using procedural parameters...Turing
equivalence is a nice tool but it's not the point.

The fact that not all languages have procedural parameters gives some
weight to the Ada position.

The fact that C, Pascal, Modula, FORTRAN, Algol, and many other languages
do have procedural parameters gives weight to the position that the lack of
procedural parameters is a shortcoming of Ada.

The argument that procedural parameters can be simulated is really
irrelevant.  The issues have to do with convenience and safety, not simple
expressive power in a theoretical sense.  (Most languages are equivalent in
that theoretical sense.)  Hence the discussion would be much more useful if
it concentrated on Ada solutions which represent something like procedural
parameters with a notation comparably concise and convenient.  Adding an
enumerated type, constructing the (unenforced!) correspondence between
enumeration values and procedures, and replacing a single procedure
invocation with a case statement over an enumeration value (assuming that
the set of procedures of interest is actually a priori enumerable!) is not
at all the same in any way of interest to a practicing programmer.  A
better answer is necessary here.
-- 
Dick Dunn	{hao,ucbvax,allegra}!nbires!rcd		(303)444-5710 x3086
   ...Simpler is better.