Re: Passing procedures as parameters to procedures.

[cis.ohio-state.edu!magnus.acs.ohio-state.edu!usenet.ins.cwru.edu!howland.]

>From article <1993May4.154040@di.epfl.ch>, by Magnus.Kempe@di.epfl.ch (Magnus 
Kempe):
> : [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;
> ....
> 
> 
> Good enough?



Nope! Unfortunately, my original A is recursive, and in particular it
is called from with D. (I realise I should have told you this!) So,
since A must be generic, D must be nested inside it (a generic
procedure can only be called from within itself).

I believe that the problem is insoluble, since B needs to be both
generic (so it can be instantiated with D) and non-generic (so it can
be an actual generic parameter of A).


Good try, though.

BTW, the original code is not mine, and I don't feel that I can post
it on the net without the author's permission (he is currently on
study leave). Trust me that I have faithfully set out the essential
elements of it.




cheers


andrew


#  Andrew Dunstan                   #   There's nothing good or bad   #
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#    adunstan@steptoe.adl.csa.oz.au #   but thinking makes it so.     #
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