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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: A few questions
Date: Thu, 12 Nov 2015 20:19:47 +0000
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Date: 2015-11-12T20:19:47+00:00
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"Randy Brukardt" <randy@rrsoftware.com> writes:

> <briot.emmanuel@gmail.com> wrote in message 
> news:aa0cf839-651e-494d-a826-c2ce31a7afd3@googlegroups.com...
>>> The "of" form is for iterating over an array or a container whose
>>> type has the Default_Iterator aspect (which gives the iterator to
>>> use).
>>
>> The main drawback, though, is that you then get a Cursor, not an
>> Element, so you still need to call the functions Element or Reference
>> to get to the actual element. This is slightly less convenient
>> (syntax-wise).
>
> Sure, but not in a case like the OP's, where the "cursor" is the
> actual data and there is no element. In that case, "of" is just
> overkill.

There's one problem for Times; how to determine when to end the loop if
the cursor is the actual data?

I ended up with

   type Cursor (Valid : Boolean := True) is record
      case Valid is
         when True =>
            Date : Ada.Calendar.Time;
         when False =>
            null;
      end case;
   end record;

where both First and Next set Valid to False if the iteration has ended.

I spent a lot too much time without giving Valid a default value; there
is an assignment, but it's hidden inside the generated code, so at the
end of the loop the discriminant changes ...

I think this may be related to the way that F552A00_Prime_Numbers
doesn't support an upper bound of 2; the loop terminates when Is_Prime
returns false, and of course 2 + 1 = 3 which .. Is_Prime.