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From: st92j0gw@dunx1.ocs.drexel.edu (Chris Papademetrious)
Subject: Package parameters in generic packages
Date: 1996/07/08
Message-ID: <4rs1vn$6t8@noc2.drexel.edu>#1/1
X-Deja-AN: 167268225
organization: Drexel University
newsgroups: comp.lang.ada
Date: 1996-07-08T00:00:00+00:00
List-Id: <comp.lang.ada>


 I am seriously confused about how package parameters are supposed to
work.  Everyone is familiar with the syntax:

generic
  with package P is new Q(<>);
package X is
...
end X;

 where a generic package itself is passed as a parameter for X so that
P inherits the generic parameter that this parameter package was
created with.  I read in "Programming in Ada 95" by Barnes that it is
a special case that when the default form (<>) is used, the formal
parameter in package Q is also visible in P.  Thus, if Q was defined
as:

generic
  type Real is digits (<>);
package Q is
..
end Q;

 then the type Real is able to be referenced as P.Real *inside* of X.
However, I was not able to reference P.Real inside of the package body
of X, only in the package *specification* of X.  Is this normal?  To
get around this, I had to do something like this in the specification:

 subtype Foo is P.Real;

 then use this Foo type in the package body of X!  Messy, messy.  What
am I not understanding?  Incidentally, this all comes into play
because I am trying to create a vectors/matrix package that supports
complex numbers, but I need access to

  Ada.Numerics.Generic_Complex_Types.Real

 inside of the package for some of the vector/matrix operations.  Any
help appreciated.  I am hoping that the entire Ada 95 community will
benefit from my work when this package is released.


-=-=-=-=-=-=-=-=-=-=-=-=-
 Chris Papademetrious
 Data Fusion Laboratory
 Drexel University
 Philadelphia, PA
-=-=-=-=-=-=-=-=-=-=-=-=-