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Re: Mathematica and Lisp

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  • Subject: [mg130056] Re: Mathematica and Lisp
  • From: Murray Eisenberg <murray at>
  • Date: Thu, 7 Mar 2013 03:59:57 -0500 (EST)
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The order of arguments of the 2-argument ArcTan seems to me merely an arbitrary choice.

I cannot imagine why anybody would make the slightest fuss about it. Unless, that is, he's just determined to find things in Mathematica to carp about.

On Mar 6, 2013, at 5:55 AM, Richard Fateman <fateman at> wrote:

> On 3/5/2013 7:54 PM, djmpark wrote:
>> Reverse the order of what? ArcTan of one argument has only one argument and
>> how can that be reversed? What has two arguments is the coordinate
>> specification {x, y} and they are not reversed in ArcTan[x, y].
>> It is the one argument form ArcTan[y/x] that seems poorly designed and would
>> probably only be used when one knows the quotient and not x and y - so there
>> wouldn't be anything to reverse.
>> From: Richard Fateman [mailto:fateman at]
>>  (simple example:  why does Mathematica reverse the order of arguments to
>> arctan of 2 args?)
> ArcTan[x,y]  in Mathematica gives the ArcTan[y/x] but in the correct
> quadrant.
> atan2 (y,x) in FORTRAN gives the arctangent of y/x). Note the order of
> arguments.
>             in C++
>             in Pascal
>             in Java
>             in Lisp  (atan y x)
>             in PHP
>             in Python v 3.3.0
>             in Ruby
> I was able to find just one programming language that agrees with the
> order in Mathematica.
> That is Microsoft's Excel. Now it could be that compatibility with Excel is
> more important than compatibility with those other languages. Google
> docs has to
> use the same order as Excel, but I think it is generally recognized as being
> compatible with an error.
> Just sayin'.

Murray Eisenberg                                    murray at
Mathematics & Statistics Dept.      
Lederle Graduate Research Tower            phone 413 549-1020 (H)
University of Massachusetts                               413 545-2838 (W)
710 North Pleasant Street                         fax   413 545-1801
Amherst, MA 01003-9305

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