[Rivet] VetoedFinalState problem

[Andy Buckley]

James Monk wrote:
> We have the same problem with wanting to exclude some leptons from the  
> FastJets projection, which also holds a FinalState and not a  
> VetoedFinalState.  I got caught up in HepMC issues with adding the  
> functionality to VetoedFinalState to remove the Z decay products, so  
> haven't yet got around to sorting out the FinalState Vs.  
> VetoedFinalState member.

Okay, so this (as well as me writing the manual) are our main blockers
for this release. It's quite a major bug, so there's no question of
releasing with this problem and then presenting a patch release. Please
coordinate among yourselves to work out who's fixing what.

> I wonder if we actually need a distinction between a FinalState and a  
> VetoedFinalState?  A VetoedFinalState without any vetoes applied is  
> the same as a FinalState, so could we not just ditch FinalState and  
> use VetoedFinalState everywhere (with an appropriate compare method so  
> it gets cached when there are no vetoes applied).

It's a valid idea, and I'm all for avoiding a proliferation of
FinalStatey projections, but let's hold off changes of that kind until
after this 1.0 release. It works without it, so let's add this to the
growing list of design ideas to re-think for version 2! (Add a ticket if
you like)

Andy