Re: bug alert!
- To: mathgroup at smc.vnet.net
- Subject: [mg25325] Re: [mg25301] bug alert!
- From: Jack Goldberg <jackgold at math.lsa.umich.edu>
- Date: Sat, 23 Sep 2000 03:35:49 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Well, something is seriously wrong with my so-called "correct"
answer. It should be (Floor[x]+1)UnitStep[x].
Sorry :>)
Jack
On Tue, 19 Sep 2000, Jack Goldberg wrote:
> Hi group:
>
> Brief report of a bug: ver 4.0x on PowerMac and Unix systems.
>
> Sum[ UnitStep[x-k],{k,0,Infinity} ] -> (1+x)*UnitStep[x]
>
> which is incorrect. The correct answer is Floor[x]*UnitStep[x].
> This error is compounded when you
>
> Sum[f[x-k]*UnitStep[x-k],{k,0,Infinity}],
>
> in that not only to you get an incorrect answer, the answer contains hidden
> variables and is total nonsense.
>
> Something is seriously at fault here.
>
>