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MathGroup Archive 1998

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Re: FactorInteger

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14423] Re: [mg14412] FactorInteger
  • From: "Carl K.Woll" <carlw at fermi.phys.washington.edu>
  • Date: Wed, 21 Oct 1998 03:32:20 -0400
  • Organization: Department of Physics
  • References: <199810181910.PAA02330@smc.vnet.net.>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Alan,

One idea is to use HoldForm. For example,

HoldForm[2^2 3^3]

displays as

2^2 3^3

Thus, one could make a function, called HoldFactorInteger, as in the
following:

HoldFactorInteger[a_Integer]:=
  Apply[Times,Apply[Power,HoldForm[Evaluate[FactorInteger[a]]],{2}],1]

The idea of the function is to wrap HoldForm around the output of
FactorInteger, but without the Evaluate, the FactorInteger function
won't evaluate. The output of FactorInteger is a list of lists, so the
Apply function replaces the inner lists with Power and the outer list
with Power.

Carl Woll
Dept of Physics
U of Washington

awhopper at hermes.net.au wrote:

> Dear Math Group,
>
> Concerning the Prime Factors of composite integers ;
>
> e.g;
>
> In[1] := 2^4 3^3 4^2
>
> Out[2] = 6912
>
> In[3] := FactorInteger[%]
>
> Out[4] = {{2,4},{3,3},{4,2}}
>
> In Mathematica 3.0 is there anyway the output of FactorInteger can be
> modified to produce the unevaluated prime factors in the usual
> exponential form ?
>
> regards,
>
> Alan Hopper
> Katoomba, Australia
> awhopper at hermes.net.au




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