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From: "Alex Angas" <wgd@adelaide.on.net>
Newsgroups: comp.lang.ada
Subject: Instantiating a generic ADT from another ADT
Date: Mon, 23 Apr 2001 09:44:34 +0930
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Date: 2001-04-23T09:44:34+09:30
List-Id: <comp.lang.ada>

Hey all, I'm having a great deal of trouble trying to instantiate a generic
list package ADT (with generic functions) from another ADT (a hash table
ADT). Can this even be done? I'm trying to create a linked list of hash
tables.

The problem is that I am declaring functions that use the as-yet undeclared
type of hash_table_list. The compiler isn't happy about just saying that
it's private so I tried to declare it at the end of the private section.
Didn't work! Compiler also isn't very happy about declaring that function to
be used by generic_list_package in the private section of hash_table.ads. I
really don't know how to do this. Here's the code:


*** hash_table.ads:

with generic_list_package;
package hash_table is
  type hash_table_list is private;

  function lookup(i : integer) return hash_table_list;
...
private
...
  function get_key(i: in hash_table_entry) return integer;
  -- this is a generic function in generic_list_package

  package hash_table_list_package is new generic_list_package(
                                     item_type => hash_table_entry,
                                     key_type => integer);

  type hash_table_list is new hash_table_list_package.item_list;
end hash_table;


*** generic_list_package.ads:

generic
  type item_type is private;     -- type stored in list
  type key_type is private;      -- type for comparing items in list

  with function get_key(item: in item_type) return key_type is <>;
  -- used for comparing keys

package generic_list_package is
  type item_ptr is private;
  type item_list is limited private;
.,.
end generic_list_package;

***

Any ideas??
Cheers, Alex.