P4estMesh: Naming of symbolic indices

[ranocha]

@sloede in #767 (comment):

I am not fully happy with the naming of the symbolic indices. I don't like the asymmetries between :one and :end or :i and :i_backwards, respectively. Maybe we use :begin instead of :one (or :first/:last)? :i_forwards instead of :i (or :forwards/:backwards)?

CC @efaulhaber

[efaulhaber]

:forwards or :backwards would only work in 2D, as there are two surface indices in 3D.
I'm okay with the other suggestions if you prefer these.

[ranocha]

@sloede: I'm also okay with

• :one: → :begin
• :i → :i_forwards
• :j → :j_forwards

[sloede]

If I understand you correctly, this is the proposal on the table:

• :begin and :end to indicate fixed indices
• :i_forwards, :j_forwards to indicate incrementing indices
• :i_backwards, :j_backwards to indicate incrementing indices

Incidentally, is it forwards/backwards or should it be forward/backward?

[ranocha]

If I understand you correctly, this is the proposal on the table:

Yes

[ranocha]

Incidentally, is it forwards/backwards or should it be forward/backward?

Both is okay for me - native speakers?

[andrewwinters5000]

Incidentally, is it forwards/backwards or should it be forward/backward?

Both is okay for me - native speakers?

forward/backward sounds better to my ear

[sloede]

OK, so the result is

• :begin and :end to indicate fixed indices
• :i_forward, :j_forward to indicate incrementing indices
• :i_backward, :j_backward to indicate decrementing indices