Re: Q: access to subprogram

[bobduff@world.std.com (Robert A Duff)]

In article <ROGOFF.96Jul23093858@sccm.Stanford.EDU>,
Brian Rogoff <rogoff@sccm.stanford.edu> wrote:
>Hi Bob,

Hi Brian,

>	While this is now straying a bit from Ada 95,

Indeed.  I hope people don't get too annoyed at us for discussing
general language design stuff.

>.. I'm curious as to 
>whether you find Pascal style iterators using downward funargs (there, I'm 
>using Lisp terminology) superior to CLU/Sather-1.0 style iterators. 

No.  When I was a Pascal programmer many years ago, I used
procedures-as-params a lot for iterators.  But CLU iterators are clearly
superior.  I don't know Sather, but from what I've read, they seem even
more superior.

>...And 
>how do the Ada 95 alternatives stack up?

Not very well, I'm afraid.  You can use generics, but you end up with a
lot of verbose junk for some simple things.  Sigh.

>... Also, were these downward funargs 
>widely used, or was there a small set of problems in which they were the ideal
>vehicle of expression, like the multidimensioal integration example? 

I'd say Pascal's downward "funargs" were widely used for iterators.  At
least in the code I saw, and the code I wrote.

>...I realize 
>in Scheme that functions are used for everything, so I am interested more in 
>the answer for Pascal and other Ada-like languages.
>
>	This is a really fascinating question in language design. 

Indeed.

>...I'd like 
>find some examples like the ones Richard O'Keefe posted, and see what the 
>best Ada 95 alternatives are. That way I can get a better sense as to how much 
>we are really missing.

Ada's generics can do *almost* everything that Pascal can do.  They
can't recurse, in Ada, like they can in Pascal.  (I needed that once.)
And they're verbose, as I said.

Smalltalk's version is pretty nice, by the way.  You don't pass
procedures -- you pass blocks.  And that avoids the annoyance of having
to name something that doesn't need or deserve a name -- it's just the
Body_Of_The_Loop, or whatever.

- Bob

P.S. I was away for more than a week, so I may have missed some answers
to my question about full closures.  Did anybody answer that?