Re: Creating a generic package with and setting its type to that of a record

[Simon Wright <simon@pushface.org>]

Andrew Shvets <andrew.shvets@gmail.com> writes:

> generic
>   type Custom_Record_Type is <>; 
> package Gener is
>   ...
>
> What I'd like to do is set the type to that of a record (which has
> some overloaded operators, such as >, < and =.)  Can this be done?  If
> so, how?

I think you are looking for generic formal subprograms[1]. Something
like

generic
   type Custom_Record_Type is private;
   with function ">" (L, R; Custom_Record_Type) return Boolean is <>;
   with function "<" (L, R; Custom_Record_Type) return Boolean is <>;
   with function "=" (L, R; Custom_Record_Type) return Boolean is <>;
package Gener is

The 'is <>' notation means you don't need to supply an actual for this
parameter if a matching one is visible at the point of instantiation.

You could instantiate it for Integer, but I'm not sure what operation
would be used if you tried "<=", for instance; the composition of your
generic actuals, or the emergent "<=" of Integer.

[1] https://en.wikibooks.org/wiki/Ada_Programming/Generics#Generic_formal_subprograms