Re: Instantiations of a generic with often encountered arguments

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2017-11-26 01:04, Victor Porton wrote:
> Is it a good practice to declare "centralized" (that is in the same package
> as a generic packages is defined in, or in a child unit) instantiations of a
> generic package with common (that is often encountered, such as Integer,
> String, etc.) generic parameters?

Yes, Ada library does so for standard types.

Sometimes a set of related generic packages is instantiated in a third 
package which is then used. E.g. you have a generic vector, matrix, 
solver defined over the same type.

> In C++ this is not a problem, because there a template is instantiated
> whenever one needs it.

Because in C++ templates are 100% macros, whereas in Ada generic 
instances can be shared, theoretically at least, and should be treated 
as real packages.

Then C++ templates have structrual matching, all instances/expansions 
with same parameters are same. It is no matter where you would expand a 
macro. Ada uses nominal matching of generic instances and they can be 
scoped.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de