From: jzakiya <jzakiya@...>
Date: 2009-12-21T06:10:06+09:00
Subject: Re: Correcting complex math

On Dec 20, 3:12 pm, Colin Bartlett <colin...@googlemail.com> wrote:
> On Sun, Dec 20, 2009 at 3:15 PM, Robert Klemme
>
> <shortcut...@googlemail.com> wrote:
> > On 20.12.2009 15:51, Colin Bartlett wrote:
>
> >> I'd also like to take the opportunity of this thread
> >> to suggest removing (!) something from Complex,
> >> unless anyone can make a good case for retaining it:
> > Done.
>
> > robert@fussel ~
> > $ allruby -r complex -e 'p Complex(1,-1) <=> Complex(-1,1)'
> > ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
> > 0
> > ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-cygwin]
> > -e:1:in `<main>': undefined method `<=>' for (1-1i):Complex (NoMethodError)
>
> Thanks for that! You've embarrassed me into installing Ruby 1.9 for Windows
> to check one or two other things! And I'm pleased to see that:
>
> require "complex" ; p  Complex(  7, 0 ) % 3
>
> ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
> Complex(1, 0)
>
> ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
> in '<main>': undefined method '%' for (7+0i):Complex (NoMethoError)
>
> And whereas in 1.8:
>   require "complex"
> c7  = Complex(  7, 0 )   #=> Complex(7, 0)
> c7n = Complex( -7, 0 )   #=> Complex(-7, 0)
> c7i = Complex(  0, 7 )   #=> Complex(0, 7)
> c7n <=> c7i   #=> 0
> c7i <=> c7    #=> 0
> c7n <=> c7    #=> 0
> require "mathn"
> c7  = Complex(  7, 0 )   #=> 7
> c7n = Complex( -7, 0 )   #=> -7
> c7i = Complex(  0, 7 )   #=> Complex(0, 7)
> c7n <=> c7i   #=> 0
> c7i <=> c7    #=> 0
> c7n <=> c7    #=> -1
>
> In 1.9 the "<=>" is not (as you pointed out) defined, so we get
> the (from my point of view) desirable "collapse" of the program,
> instead of the (from my point of view) inconsistent results of 1.8.
>
> This post from July 2009 seems relevant:http://redmine.ruby-lang.org/issues/show/1712
> .. writes
>
> > |1.8's Complex had a modulus operator (%); 1.9's doesn't, and attempts to use it
> > raise a NoMethodError for #floor because it falls back to Numeric#%
> > which needs #floor. Is this omission intentional? If so,
> > could an appropriate NoMethodError be raised instead?
> > If not, I'd appreciate knowing so I can write the specifications.
>
> I don't think there's natural definition of modulo on complex numbers,
> so that we should undefine % method.  We might need to do something
> for compatibility's sake.  Opinion?
>                                                         matz.
>
> Does anyone know of any other threads on this?
>
> *** OffTopic ***
>   > remember.guy do |as, often| as.you_can - without end
> I doubt if I understood 5% (if that) of the technical parts of Guy
> Decoux's posts.
> Which is to say, given his terse style, almost every part of his posts.
> But even I could detect a rather endearing underlying humour in those posts.

I see in Python % is invalid for complex numbers.

http://www.webreference.com/programming/python/
http://docs.python.org/reference/expressions.html