Defined in The verb object Return value The value of the monadic type if present otherwise the user provided fallback value Call signatures Supply a fallback for the failure state keeping the carrier Unlike the member value_or which eliminates the carrier and yields a value the pipeline form returns the carrier engaged with either its own value or a fallback built in place from the arguments Where the value type is void value_or takes no arguments at all Rejected on choice and just which can never lack a value on the identity expected the fallback stays constrained yet dead generic code compiles the branch is never taken Use through the fn value_or nielbloid value_or_t value_or 1 Substitutes a fallback for the dead state x | value_or v template <typename Args> constexpr auto operator Args && args const > functor<value_or_t Args && > 1 Supply a fallback for the failure state keeping the carrier return A functor that will substitute the fallback where the value is missing args Args && Arguments the fallback value is built from in place