Defined in The verb object Call signatures Return value A monadic type of the same kind Map the value of the monadic type keeping the carrier s shape The callable s result becomes the new value in the same carrier family a bare non monadic callback result belongs here rather than to and_then Over a copack valued carrier the callable is dispatched per alternative heterogeneous branch results joining into a normalized copack In the pipeline form only a copack result over a just operand is promoted to the choice over the same alternatives Use through the fn transform nielbloid transform_t transform 1 Maps the value staying in the carrier x | transform f constexpr auto operator auto &&fn const > functor<transform_t decltype fn > 1 Map the value of the monadic type keeping the carrier s shape return A functor that will execute the function on the value fn auto && The function to execute on the value