Я ☞ Operators ☞ yoi

Precedence: 7

`yoi` - [Y]oneda c[O]variant [I]dentity

How to read: modify the first argument covariantly, ignore the second one.

Works the same way as yo but for a 1-nd argument of a functor.

 `yo` :  t a  `AR_` into (from a o)  (t o)
`yoi` : t a _ `AR_` into (from a o) (t o _)