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From: "Ayende Rahien" <Dont@spam.me>
Newsgroups: comp.lang.ada
Subject: Re: Problem trying to implement generics.
Date: Thu, 12 Apr 2001 15:15:45 +0200
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<tmoran@acm.org> wrote in message
news:zJ7B6.11026$ix4.8084250@news1.rdc1.sfba.home.com...
> >I've just started to learn Ada, and I've some problem solving some
problems.
>   If you are learning in a course, asking the instructor will be much
> faster than asking here.  Assuming you are trying to learn just from
> a book:

I'm learning from a book.


> >Here is the error:
> >bintree.adb: Error: line 43 col 25 LRM:8.4(1), Binary operator ">"
between
>   Without seeing line 43 (or any lines) of bintree.adb it's a little
> hard to see what's going on, but, as the compiler suggests, a "use"
> or "use type" might be what you need.

Here is the line:
if current.sorted_by > sort then

What does use type does? How do I use it?

> >procedure insert(insert_this : in data_type; Sort : in sort_by) is
> >Here is the error this line produce:
> >bintree.adb: Error: line 107 col 12 LRM:3.11.1(7), subprogram body is a
> >homograph of another subprogram which does not require a completion,
>   That sounds like you have two different "insert" subroutines which
> look the same in calling parameters so if the compiler saw
>  insert(a,b);
> it wouldn't know which one to call.

Yes, I found & fixed it, thanks.

> >bintree.adb: Error: line 150 col 18 LRM:3.10.2(23&31), The prefix to
'ACCESS
> >must be either an aliased view of an object or denote a subprogram with a
>   Like the message says, the thing before 'access must be aliased.  Given
>   type node is record
>     Data : Data_type;
>     ...
>   type node_access is access all Node;
>     ...
>   result : node_access ...
>   ...  result.data'access;
> you see that "result.data" is defined as not aliased.  Try
>     Data : aliased Data_type;

That solved the problem, but why? What does aliased mean?

> >Also I've a trouble using Root variable in a function that is undefied in
>   Is the Root variable defined before the function that uses it?

Yes, it's defined here:
type Binary_Tree is new Ada.Finalization.controlled with record
   root: Node_access := null;
  end record;

Which is on the ads file, and other functions doesn't seem to have trouble
finding it.
The only thing I can think of is that this doesn't work because the function
is not declared on the ads file.