Re: How to NOT give new default to parameter of generic procedure parameter?...

[collard@software.org (David Collard)]

In article <1991Feb14.224435.1512@software.org> stluka@software.org (Fred Stluka) writes:
> Here's one for the language lawyers.  I don't think there is
> a way to do this.  Someone please tell me that I'm wrong.
> 
> From within a generic body GEN, I want to call a procedure PROC1 
> which was was passed in as a generic parameter PROC.  I want to 
> make the call without specifying any parameters, allowing all of 
> them to default to the default expressions specified in the 
> declaration of PROC1.  I also do not want to re-specify the default
> expressions in my declaration of PROC as a generic formal parameter 
> to GEN, because this would override the defaults of PROC1 which may
> someday be changed.
> 

Are either of these options better?  the first takes in your constant
as a generic formal and the second takes in a visible function 
as a generic formal (default).  

--  (1)  --
 generic
   default_for_x : integer;
   with procedure proc1(x : integer := default_for_x);
 procedure gen;

 procedure gen is
 begin
   proc1;
 end gen;
 
 with gen;
 with Text_IO; use Text_IO;
 procedure boss is
   def : integer := 1;
   procedure proc(x : integer := 1) is
   begin
     put_line(integer'image(x));
   end proc;
   procedure mygen is new gen(proc1, def);
 begin
   mygen;
 end boss;

\f
--   (2)   --
generic
  with function default_for_x return integer is <>;
  with procedure proc1(x : integer := default_for_x);
procedure gen;

procedure gen is
begin
  proc1;
end gen;

with gen;
with Text_IO; use Text_IO;
procedure boss is
  function default_for_x return integer is begin return 1; end;

  procedure proc(x : integer := 1) is
  begin
    put_line(integer'image(x));
  end proc;
  procedure mygen is new gen(proc1 => proc);
begin
  mygen;
end boss;



-- 
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D. Thor Collard                      Internet: collard@software.org
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