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MathGroup Archive 2006

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RE: pretty output with HoldForm

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70455] RE: [mg70425] pretty output with HoldForm
  • From: "David Park" <djmp at earthlink.net>
  • Date: Tue, 17 Oct 2006 02:58:12 -0400 (EDT)

Peter,

Download the free ExpressionManipulation package at my web site and then use
the EvaluateAtPattern command. (I didn't know if you wanted to sum from 0 or
from 1.)

Needs["Algebra`ExpressionManipulation`"]

kl[n_] := HoldForm[ 1/(2n + 1) - 1/(4n + 2) - 1/(4n + 4)]

Sum[kl[n], {n, 0, 5}]

Sum[kl[n], {n, 0, 5}] // EvaluateAtPattern[_Times];
% // EvaluateAtPattern[_Times]

HoldForm[1 - 1/2 - 1/4] +
  HoldForm[1/3 - 1/6 - 1/8] +
  HoldForm[1/5 - 1/10 - 1/12] +
  HoldForm[1/7 - 1/14 - 1/16] +
  HoldForm[1/11 - 1/22 - 1/24] +
  HoldForm[1/9 - 1/18 - 1/20]

(I'm a little disconcerted that I had to apply it twice. The routine is also
in Tensorial.)

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/



From: Peter Breitfeld [mailto:phbrf at t-online.de]
To: mathgroup at smc.vnet.net


I want to get the following output for the series:

(1 - 1/2 - 1/4) + (1/3 - 1/6 - 1/8) + (1/5 - 1/10 - 1/12) +
  (1/7 - 1/14 - 1/16) . . .

What I did was

kl[n_]:=HoldForm[ 1/(2n+1)-1/(4n+2)-1/(4n+4)]

then I enter eg:

reihe= Sum[kl[n],{n,1,5}]

This works quite good, but the fractions are completely unevaluated
(because of HoldForm, I know) and display as

     1
----------
4 2 + 2

But I want them displayed as

 1
--
10

Is there a way to evaluate parts inside a HoldForm, so that the
fractions are evaluated but not the sums?

Gruss Peter
--
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de



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