bug alert!

*To*: mathgroup at smc.vnet.net*Subject*: [mg25301] bug alert!*From*: Jack Goldberg <jackgold at math.lsa.umich.edu>*Date*: Tue, 19 Sep 2000 03:45:22 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

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.