Usage of angle vs. direction

[zhardy-lanl]

Originated from discussion on #100.

[ragusa]

angle is a misnomer in most of the code. often, what is meant is a direction, which, as we all know, takes 2 angles to be fully defined in 2d and 3d.
I am of the strong opinion that angles should become directions. My only (small) hesitation is angle_set versus direction_set because angle_set rolls better off the tongue.

[zhardy-lanl]

I tend to agree with this. Angle seems like a (theta, varphi) pair whereas direction seems like a vector. We could call it an OrdinateSet which sounds better then DirectionSet in my opinion.

[wdhawkins]

I agree. We've gotten in the habit of saying angles, angle sets, etc. when we really mean direction. I have no strong feeling s on nomenclature. I like Zach's OrdinateSet suggestion.