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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Trouble with "operation can be dispatching in only one type"
Date: Wed, 13 Aug 2014 23:01:42 +0300
Organization: Tidorum Ltd
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Xref: number.nntp.dca.giganews.com comp.lang.ada:188435
Date: 2014-08-13T23:01:42+03:00
List-Id: <comp.lang.ada>

On 14-08-13 22:23 , Victor Porton wrote:
> I defined two tagged types T1 and T2 in some package.
> 
> I need a function in the same package:
> 
> not overriding function F (Stack: T1) return T2;
> 
> The compiler complaints:
> 
> operation can be dispatching in only one type
> 
> My current workaround is to define it instead as:
> 
> not overriding function F (Stack: T1'Class) return T2;
> 
> But this is a hack. Can I define this function in the right way? (I want it 
> to be dispatching only in T1, not T2.)

To be dispatching in T1, but not in T2, it should be

   function F (Stack : T1) return T2'Class;

If the use of 'Class to prevent dispatching is a problem for you,
another way is to put the two type declarations in different packages.

A function F can be dispatching only in the type declared in the same
package as F. For example, if T2 is declared in a different package than
T1 (including a package nested within the package that declares T1) then
you can declare function F (Stack : T1) return Some_Pkg.T2 and it will
dispatch only in T1 (assuming that T1 and F are declared in the same
package declaration).

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .