Defined in What a verb call such as returns and the point at which the pipeline is open to extension a verb of your own defined outside the library pipes exactly like the built in ones A verb is an empty default constructible type whose returns a over itself and whose nested does the work is the smallest example to read Feeding a carrier into a step fn and_then f operator functor apply fn discard_t A pipeline step waiting for a carrier the verb and its arguments as one value What a verb call such as fn and_then f returns a description of the operation executed only when a carrier is piped into it with operator| The arguments are stored as as_value_t prescribes rvalues by value non empty lvalues an immovable callable among them by reference friend constexpr auto operator| some_monadic_type auto &&v auto &&self 1 Feeds a carrier into the pipeline step return Whatever the verb s apply returns for this carrier and the stored arguments v some_monadic_type auto && The carrier in any value category self auto && The step this functor