Compound FkTables

[alecandido]

Soon we'll have to make "compound" FkTables, and since the new FkTable format lies in pineappl, then we have to add in here the support for the operations described in https://docs.nnpdf.science/data/th-data-files.html#compound-file-format, that are:

• [ ] NULL: 1 -> 1 trivial operation
• [ ] ADD: 2 -> 1 sum bins in pairs
• [ ] SMT: n -> 1 sum bins in groups
• [ ] SMN: 4 -> 1 normalized sum
• [ ] ASY: 2 -> 1 compute the asymmetry (difference over sum)
• [ ] COM: 2n -> 1 combination (sum of the first half over sum of the second)
• [ ] RATIO: 2 -> 1 ratio of the first over the second

All the operations are done binwise.

[alecandido]

Maybe this is fake, since "compound" might be applied by validphys and not apfelcomb, so we do not have to implement anything.

[alecandido]

Without "maybe": these operations are only available after convoluting with a PDF, so they can not be implemented at the level of pineappl.

Thus I close this issue.