mathematical/mekso binary operator: vector or function inner product over a field; the inner product of A and B over field C

The field is usually defined or implicitly clear from context. May be generalized to higher tensors over fields and which have many (or less) entries; in this case, it is tensor multiplication followed by contraction.

- ci'o'au
- mekso operator (binary): projection function; the Bth term/entry ("element") of tuple A