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Re: Re: FactorInteger Print Formatting
*To*: mathgroup at christensen.cybernetics.net
*Subject*: [mg767] Re: [mg694] Re: [mg650] FactorInteger Print Formatting
*From*: tiggj at iswaps.lonnds.ml.com (Jason Tigg SWAP GROUP ANALYST X2312 LDN)
*Date*: Tue, 18 Apr 1995 00:58:05 -0400
Hi,
this may be what you want
In[1] := Format[ factorform[a_List] ] :=
StringTake[ Apply[ StringJoin, Map[gform, a]], {1,-2}];
gform[{b_,1}] := ToString[b] <> "*";
gform[{b_,n_}] := ToString[b] <> "^" <> ToString[n] <> "*";
In[2] := 2^12 5^5 199
Out[2] = 2547200000
In[3] := factorform[ FactorInteger[%]]
Out[3] = 2^12*5^5*199
jason
>
> Dear Alan:
>
> Here is a clue. It is not exactly what you asked for, and it still needs
> an automatic way to generate the [[4]] at the end, but I think it is some
> progress.
>
> In[23]:= Trace[FactorInteger[400] /. {a_,b_}->a^b][[4]]
>
> 5 2
> Out[23]= {2 , 4 }
>
> If you try to go beyond this kind of list output to the product form you
> asked for, the automatic exponent evaluation machinery takes over and
> destroys all progress. This is closely related to a question I asked
> recently, which I suspect has no answer; viz: How do you prevent
>
> In[34]:= Sqrt[8]
>
> Out[34]= 2 Sqrt[2]
>
> I think what we need is an new option, like AnswerForm->pattern, which
> would stop evaluation if the desired pattern is created anywhere along the
> evaluation chain.
>
> Has anybody given any thought to this, WRI?
>
> Regards- Martin
>
> >Could anyone suggest a neat way to reformat the output of
> >FactorInteger into a more usable print format?
> >
> >FactorInteger[n] gives a list of prime factors of the integer n
> >in ascending order, together with their exponents viz:
> >
> > FactorInteger[900] produces the list {{2,2},{3,2},{5,2}}
> >
> >What I need is a function called say factorform[list] such that:
> >
> > Print[ factorform[{{2,2},{3,2},{5,2}}] ] produces 2^2*3^2*5^2
> >
> >Ideally exponents equal to 1 would be suppressed so that when
> >
> > ff = FactorInteger[30] produces {{2,1},{3,1},{5,1}} then
> >
> > Print[factorform[ff]] would give 2*3*5 instead of 2^1*3^1*5^1 and
> >
> > Print[factorform[FactorInteger[2^6*3*5^2*7]]] would give 2^6*3*5^2*7
> >
> >A procedural solution is possible, but I was unable to create a simple
> >function which would give the desired result.
> >
> >
> >Alan Powell POWELLA at delphi.com
>
>
>
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