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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Problem with generic linked list package
Date: Sun, 10 Aug 2014 09:22:53 +0100
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Date: 2014-08-10T09:22:53+01:00
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Laurent <daemon2@internet.lu> writes:

> Yes indeed if Element would be a record then insert_in_order wouldn't
> work as it is. Because "<" and "=" don't exist for this type. Perhaps
> if I compared the components of the record I would but for now I don't
> see how I would do that. Problem for later when I have to use my
> package for a real program.

   type Rec is record
      B : Boolean;
      I : Integer;
   end record;
   function "<" (L, R : Rec) return Boolean is
   begin
      return L.I < R.I;
   end "<";

and similarly for "=".

I've found it's less confusing for me if I don't actually call these
functions "<", "=" but rather Less_Than, Equals. You lose the (minor)
inconvenience of being able to use the default comparison when
instantiating your generic, but gain clarity. This is presumably why we
have Ada.Strings.Less_Case_Insensitive and Equal_Case_Insensitive;
if they were called "<", "=" there could easily be ambiguity with the
default String subprograms.