Defined in The verb object Call signatures Return value A monadic type of the same kind Intercept the failure and force a transition back to the success state The dual of fail On expected the callback maps the error into the operand s existing value type never widening it where the value type is void the callback observes the error and must return void On optional the callback is invoked with no arguments the empty state carries no error value Rejected on choice and just which have no failure to recover from on the identity expected the operand passes through and the callback is never instantiated Use through the fn recover nielbloid recover_t recover 1 Supplies a value for the dead state x | recover f constexpr auto operator auto &&fn const > functor<recover_t decltype fn > 1 Intercept the failure and force a transition back to the success state return A functor that will recover the monadic type fn auto && The function to produce the replacement value from the error on expected from no arguments on optional