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Date: 4 May 93 13:45:33 GMT
From: cis.ohio-state.edu!pacific.mps.ohio-state.edu!linac!uwm.edu!cs.utexas.edu
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di.epfl.ch!Magnus.Kempe@ucbvax.  (Magnus Kempe)
Subject: Re: Passing procedures as parameters to procedures.
Message-ID: <1993May4.154040@di.epfl.ch>
List-Id: <comp.lang.ada>

In article <1s5gae$kr4@huon.itd.adelaide.edu.au>, andrewd@winnie.cs.adelaide.ed
u.au (Andrew Dunstan,,2285592,) writes:
:
: As I pointed out in this group about a year ago, there are some things
: that you want to be able to do that you just can't with generics. If
: anybody can provide me with a good, clean, Ada equivalent of the
: following Pascal code, I'll send him/her (first winner only!) a good
: bottle of Australian red wine (damn this Beaujolais business!).
: [Pascal code omitted]

The solution is to make "D" visible.


package Wrap_AD is

  procedure D;
  
  generic
    with procedure B;
  procedure A_G;

end Wrap_AD;

package body Wrap_AD is

  procedure D is begin null; end D;
  
  procedure A_G is
  begin
    B;
  end A_G;

end Wrap_AD;


generic
  with procedure Y;
procedure X_G;

procedure X_G is
begin
  Y;
end X_G;


procedure X is new X_G (Wrap_AD.D);

procedure A is new Wrap_AD.A_G (X);

...
A;
...


Two drawbacks: if D needs to access local variables of A_G, these
variables must be made global (but may be hidden in the body of
Wrap_A); the parameter B to A_G need not call D, but you may consider
it a "feature", a more powerful variant.

Good enough?
-- 
Magnus Kempe                "No nation was ever drunk when wine was cheap."
magnus@lglsun.epfl.ch                                   -- Thomas Jefferson