val
(&&&) : ('a, 'b) t -> ('a, 'c) t -> ('a, 'b
* 'c) t
Compose two filters such that both are applied to the same value,
and their corresponding results are paired in a tuple. This filter
will fail if any of the two argument filters fails.
val
(>>>) : ('a, 'b) t -> ('b, 'c) t -> ('a, 'c) t