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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Arctan: to use with single or with double arguments?
Date: Sat, 11 Feb 2012 16:47:23 +0000
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Date: 2012-02-11T16:47:23+00:00
List-Id: <comp.lang.ada>

Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:

> On 11.02.12 16:29, Simon Wright wrote:
>> AdaMagica<christ-usch.grein@t-online.de>  writes:
>>
>>> It's a severe bug to use positional association for Arctan!
>>
>> Only a bug if you get it wrong. Otherwise it's a meta-bug.
>>
>> Not sure that Arctan (Y =>  X, X =>  Y) is exactly _clear_.
>
> No clarity at all when the brain switches between coordinate
> system conventions, row or column major order, and similar
> non-Ada ways of expressing things.  Since the semantics of
> any program calling Arctan is not changed if the parameter
> name X becomes <<unambiguously-denoting-what-we-mean>>, thus
> since there will be an absolutely safe change set if such
> a name were introduced, isn't it about time to get rid of
> names that only a high school delusion holds up against?

In Ada2012,

   with Ada.Numerics.Elementary_Functions;
   package Naval_Angles is
      function Bearing (Northings : Float;
                        Eastings  : Float) return Float is
         (Ada.Numerics.Elementary_Functions.Arctan (Y => Eastings,
                                                    X => Northings));
   end Naval_Angles;

(not sure that 'bearing' is the right word, since the same coordinate
system is used for 'heading' and 'course' ...)