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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Unconstrained array aggregation..sq. peg into round hole?
Date: 1996/03/21
Message-ID: <EACHUS.96Mar21185700@spectre.mitre.org>#1/1
X-Deja-AN: 143660876
references: <4ihrvo$hs5@dfw.dfw.net> <EACHUS.96Mar19201632@spectre.mitre.org>
organization: The Mitre Corp., Bedford, MA.
newsgroups: comp.lang.ada
Date: 1996-03-21T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <DoJqI0.51n@world.std.com> bobduff@world.std.com (Robert A Duff) writes:

  > Right, except you have to give a constraint.  Array-of-unconstrained
  > array is illegal.

   Not really, but you have to put two records in the middle to make
it work:

   subtype Limited_Subscripts is Natural range 1..1000;

   type Real_Array is array (Limited_Subscripts range <>) of Float;

   type Inner_Wrapper is (First: Integer := 1; Last: Integer := 0) is record
     B: Real_Array(First..Last);
   end record;

   type Outer_Wrapper is 
     A: Inner_Wrapper;
   end record;
 
   type Ragged_Table is array (Natural range <>) of Outer_Wrapper;

   I never understood why, if this useful and used feature was in Ada
83 and Ada 95, you have to go through all this semantic sugar to create
the ragged array type.  To keep novice users from trying it?   

   (The Limited_Subscripts subtype is so that this will work on all
implementations including those that "allocate the maximum" for this
type of subcomponent.)

--

					Robert I. Eachus

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