Re: Kernel Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg54943] Re: Kernel Problem
- From: Peter Pein <petsie at arcor.de>
- Date: Mon, 7 Mar 2005 02:10:27 -0500 (EST)
- References: <d0denl$lfr$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Dana DeLouis wrote:
> Hello. I'd like to ask a question. The function below shuts down my
> Kernel. Is it just me, or is this reproducible on other Windows machines.
> Thanks for any feedback.
>
> Needs["NumberTheory`NumberTheoryFunctions`"]
>
> Information[QuadraticRepresentation]
>
> "QuadraticRepresentation[d, n] gives {x, y}, where x^2 + d y^2 = n for \
> positive d and odd n."
>
> QuadraticRepresentation[12, 9]
>
> (Problem, and the Kernel shuts down!)
>
> TIA
> Dana DeLouis
>
Simply define your own function:
In[1]:=
QuadRep[d_, n_, sel_:{First, #1 & }] :=
If[Length[#]<2,{},#]&@
Flatten[
Extract[#1, (Position[#1, sel[[1]][#1], 1, 1] & )[sel[[2]] /@ #1]] &
[Block[{x, y, Null}, {x, y} /.
{ToRules[Reduce[{x^2 + d*y^2 == n && x>=0&&y>=0},
{x, y},Integers]]}]],
1]
In[2]:= QuadRep[12,9]
Out[2]= {3,0}
from the Mathematica documentation:
In[3]:= QuadRep[3,13*31*61*Prime[10^7]]
Out[3]= {778,1212545}
or select the solution with the smaller of {x,y} becoming maximal:
In[4]:= QuadRep[3,13*31*61*Prime[10^7],{Max,Min}]
Out[4]= {1118614,1026239}
This is just a quick hack and might need further verification.
--
Peter Pein
Berlin