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MathGroup Archive 2005

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Re: Eliminating Annoying Minus Signs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58770] Re: [mg58756] Eliminating Annoying Minus Signs
  • From: yehuda ben-shimol <bsyehuda at gmail.com>
  • Date: Sun, 17 Jul 2005 13:03:15 -0400 (EDT)
  • References: <76e8f81805071705503c70daa4@mail.gmail.com> <NDBBJGNHKLMPLILOIPPOIEHEEJAA.djmp@earthlink.net>
  • Reply-to: yehuda ben-shimol <bsyehuda at gmail.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi David,
Although not documented it seems that both Numerator and Denominator
are listable so
(-Numerator[#])/(-Denominator[#])&[test]
or
test//(-Numerator[#])/(-Denominator[#])&
 will do the same without mapping.
yehuda

On 7/17/05, David Park <djmp at earthlink.net> wrote:
> Yehuda,
> 
> Thanks. That seems pretty good.
> 
> We could turn this into a routine that could be mapped onto terms more
> generally in an expression.
> 
> NDSignSwitch = (-Numerator[#])/(-Denominator[#]) &;
> 
> test = {-((2*x)/(-1 + z)), -((2*y)/(-1 + z)), -1};
> 
> NDSignSwitch /@ test
> {(2*x)/(1 - z), (2*y)/(1 - z), -1}
> 
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
> 
> 
> 
> From: yehuda ben-shimol [mailto:bsyehuda at gmail.com]
To: mathgroup at smc.vnet.net
> 
> Hi David,
> How about
> (- Numerator /@ test)/(- Denominator /@ test)
> this is not error prone.
> I'm almost certaint that there is more efficient way of doing this.
> I'll try to find it later
> regards
> yehuda
> 
>


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