Re: Re: Just another bug in MMA 3.0
- To: mathgroup at smc.vnet.net
- Subject: [mg7637] Re: [mg7491] Re: [mg7431] Just another bug in MMA 3.0
- From: Alistair.Windsor at vuw.ac.nz (Alistair.Windsor at vuw.ac.nz)
- Date: Fri, 20 Jun 1997 16:16:10 -0400 (EDT)
- Organization: Victoria University of Wellington, New Zealand
- Sender: owner-wri-mathgroup at wolfram.com
In article <5nqru3$l5j at smc.vnet.net>, koehler at math.uni-bonn.de (Kai
Koehler) wrote:
> In article <5nfpv3$5qp at smc.vnet.net>, Paulo Mouat
<mouat at mail.telepac.pt> wrote:
>
> > Kai Koehler wrote:
>
> > > Sum[Sum[Log[Log[k+j]],{k,1,n}],{j,1,5}]
> > >
> > > gives
> > >
> > > 5*Sum[Log[Log[k + j]], {k, 1, n}].
>
> > If you want to do a multiple sum, the input should read
> >
> > Sum[Log[Log[k+j]],{k,1,n},{j,1,5}]
> >
> > What you have typed is a simple sum over k with a function that has an
> > unknown j. The j on the outer Sum is a dummy variable, with no
> > relation to the one in Log[k+j].
> >
> > This is not a bug. Mathematica simply interpreted what you did type,
> > which is not quite what you intended to do.
>
> If this where true,
It is.
> Sum[Sum[j,{k,1,n}],{j,1,5}]
>
> should give 5 n j as output.
No have a look at what he typed again. =>Sum[Log[Log[k+j]],{k,1,n},{j,1,5}] <=.
Here both iterator variables appear in the outer level of the Nested Sums.
In what you hve typed they appear in separate levels. If you were to
write Sum[Sum[j],{k,1,n},{j,1,5}] you would indeed get 5 n j. There is no
bug here. The iterator j is a local variable assign a unique hash and is
hence different from the j inside the sum.
>Instead you get 15 n (correctly, IMHO).
> Also, in StandardForm, the difference between
--
Alistair Windsor
Mathematics Graduate Student
Victoria University of Wellington
New Zealand