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Re: HoldForm

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68107] Re: [mg68094] HoldForm
  • From: "Bharat Bhole" <bbhole at gmail.com>
  • Date: Mon, 24 Jul 2006 00:55:50 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Bruce,

A simple modification of your program gives the desired result. Basically,
perform A+(-B) rather than performing A-B. So your code will look like,

A = {{1, 2}, {3, 4}};

B = {{5, 6}, {7, -8}};

Map[MapThread[HoldForm[#1 + #2] &, {A[[#]], -B[[#]]}] &, Range@2]

As desired, the output is {{1 - 5, 2 - 6}, {3 - 7, 4+8}}.

I am not sure why HoldForm treats + and - differently. It performs addition
but not subtraction in the sense that,

In: HoldForm[2+ (-3)]
Out: 2-3

In:HoldForm[2 - (-3) ]
Out: 2 - - 3

Bharat.




On 7/23/06, Bruce Colletti <vze269bv at verizon.net> wrote:
>
> Re Mathematica 5.2.0.0.
>
> This code displays the component differences of matrix subtraction (A-B):
>
> A = {{1, 2}, {3, 4}};
>
> B = {{5, 6}, {7, -8}};
>
> Map[MapThread[HoldForm[#1 - #2] &, {A[[#]], B[[#]]}] &, Range@2]
>
> As desired, the output is {{1 - 5, 2 - 6}, {3 - 7, 4--8}}.
>
> Two questions:
>
> - What's a better way to do this?
>
> - How can I replace the -- by +?
>
> Thankx.
>
> Bruce
>
>
>


-- 
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