Path: utzoo!mnetor!uunet!mcvax!enea!sommar
From: sommar@enea.se (Erland Sommarskog)
Newsgroups: comp.lang.misc
Subject: Re: Iterators
Message-ID: <2944@enea.se>
Date: 30 Mar 88 07:58:16 GMT
References: <1147@jenny.cl.cam.ac.uk> <2913@enea.se> <111@gannet.cl.cam.ac.uk>
Reply-To: sommar@enea.UUCP(Erland Sommarskog)
Followup-To: comp.lang.misc
Organization: ENEA DATA AB, Sweden
Lines: 24

Stephen Crawley (scc@cl.cam.ac.uk) writes:
>However, Ada does allow you to use procedures as parameters to a generic
>package.  As Erland pointed out, this allows you to construct iterators.
>[It is sad that Ada forces you to go to the trouble of constructing a
> generic package for a data structure you want to iterate over.]

Minor correction: A package like a tree handler should always be generic. 
But if Ada had had procedure parameters, we wouldn't have been forced
to declare the iterator as a generic procedure.
  I don't really want to go into the debate on generic vs. "real"  
procedure parameters. I can imagine that the Ada designers felt 
procedure parameters as redundant aside with procedures as generic
parameters. But I'm not really fond of declarations like
   Generic 
      With procedure A(P1 : T;
                       P2 : T2);
   Procedure B;                       
Together with the instantiation this becomes unnecessarily verbose.
The compiler and library overhead is also greater for generics.

-- 
Erland Sommarskog       
ENEA Data, Stockholm        
sommar@enea.UUCP