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From: mheaney@on2.com (Matthew Heaney)
Newsgroups: comp.lang.ada
Subject: Re: Charles: missing default values
Date: 14 Nov 2002 08:16:56 -0800
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porton@ex-code.com (Victor Porton) wrote in message news:<3dd32396$0$308$bed64819@news.gradwell.net>...
> It is reasonable to add default values to the arguments of
> many functions in charles, e.g. Genereic_Find for vectors would
> become:
> 
> generic
>   with function Predicate (Element : Element_Type)
>     return Boolean is <>;
> function Generic_Find 
>      (Container : Container_Type;
>       First     : Index_Type'Base := First(C);
>       Back      : Index_Type'Base := Last (C)) return Index_Type'Base;

This won't compile.  Where is C defined?  

This isn't even correct, because the default value for Back is Last
(C), which is incorrect.

Note that there is a non-generic version of Find, that works by
comparing elements using the equality operator for Element_Type.

If you want an instantiation of Find that accepts only the container
as a parameter, then why don't you simply use a nesting subprogram:

function Find (V : Vector_Subtype) return Index_Subtype'Base is
   procedure Find is new Generic_Find (Predicate);
begin
   return Find (V, First (V), Back (V));
end;

Note also that this is a linear search.  If your vector is sorted,
then you should be using Binary_Search or Lower_Bound.