Re: Generic default parameters

[Preben Randhol <randhol+abuse@pvv.org>]

On Fri, 10 May 2002 14:27:39 -0500, Randy Brukardt wrote:
> 
> The point of course is to provide defaults for some (not all)
> parameters, so the "package" you're talking about would have to be
> generic.
> 
> The case that brought this up is something like:
> 
>     generic
>         type Element_Type is private;
>         type Count_Type is (<>) use Natural;
>     package Lists is ...
> 
> Generally, the default Count type is sufficient. But there may be
> occassions where some user-defined type would be valuable. A typical
> instantiation would look like:
> 
>     package My_List is new Element (Some_Record);
                             ^^^^^^^
                             Lists ?

> To get that with a package, you'd have to have a generic package
> wrapper:
> 
>     generic
>         type Element_Type is private;
>     package List_with_Natural_Count is
>         package List is new Lists (Element_Type, Natural);
>     end List_with_Natural_Count;
> 
> and then you would have complications in naming the items in the
> instantiation (especially if you do not want to use a "use clause" on
> the package). The net effect (either way) is to make it harder to
> create a general component that is also relatively easy to use.


OK I see.

-- 
"Jeg tror nordmenn har glemt hvordan de tilbreder fisk. De er mest
 opptatt av firkantet fisk."
  --  Kristian Kristiansen, yrkesfisker, aftenposten.no 19/04/02