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Newsgroups: comp.lang.ada
Subject: Re: Ada 95 ARCTAN function
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From: Keith Thompson <kst-u@mib.org>
Organization: None to speak of
Date: Sun, 04 Mar 2007 13:16:57 -0800
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Date: 2007-03-04T13:16:57-08:00
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"Adam Beneschan" <adam@irvine.com> writes:
> On Mar 1, 11:38 am, Jacob Sparre Andersen <spa...@nbi.dk> wrote:
>> I don't know where I can find the corresponding specification for the
>> C function atan2(), so I can't give you a proper comparison.
>
> The Unix "man" page for atan2 has some information.  It's not as
> detailed as the Ada manual, because after all this is C and providing
> specific details would infringe on the inalienable right of C
> programmers to shoot themselves in the foot.  However, the man page
> I'm looking at does say:
>
> (1) that the result is between -pi and pi (inclusive), and
>
> (2) the signs of both arguments are used to determine the quadrant of
> the result.
>
> So I'd guess that the semantics are probably the same.

The C99 standard says:

    The atan2 functions compute the value of the arc tangent of y/x,
    using the signs of both arguments to determine the quadrant of the
    return value. A domain error may occur if both arguments are zero.

    The atan2 functions return arctan y/x in the interval [-pi, +pi]
    radians.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"