[Rivet] New projection method names without "projection"

[Andy Buckley]

Hi,

As some of you at the MCnet Computing School last week (which was 
excellent, by the way) know, I think we made a mistake when we used the 
word "projection" to name a concept in Rivet.

We're too far down the rabbit-hole to completely reverse that now, but 
we can reduce the number of times that normal users have to encounter 
the word "projection".

The main such methods are defined in ProjectionApplier. And the main two 
that users will actually encounter are addProjection and 
applyProjection. I think it could be nice to define aliases for at least 
these, and probably also for the templated getProjection methods.

For addProjection, the "Projection" part of the name is redundant 
because the argument type is an object derived from Projection. But I 
don't think "add" is a very clear name anyway, so maybe something like 
register(myproj, "MyObs") would be better? We could have "add" as 
another alias to ease the transition from addProjection.

For both applyProjection and getProjection (the templated methods only, 
I suggest), the "Projection" part is again redundant. So 
apply<MyProj>(evt, "MyObs") and get<MyProj>(evt, "MyObs") are a bit 
neater. But I am also tempted to try and ease that awkward templating 
syntax a little, to make the command read like English: 
applyAs<MyProj>(evt, "MyObs") and getAs<MyProj>(evt, "MyObs"). Thoughts?

Opinions on all the above are more than welcome. I'm not fixed on any of 
the above proposals, but would like to get rid of the "projection" word 
from most people's Rivet experience, if possible! Whatever we decide on 
is trivial to implement, so it'll easily go into the 2.5.x series, with 
full backward compatibility.

Cheers,
Andy

-- 
Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow