Scan< Devices::Cuda, Type >::perform only allows vector types but not array. The main issue seems to be mismatch of type alias, in scan `using RealType = typename Vector::RealType;` is declared. vector uses the alias `using RealType = Real;` but array uses the alias `using ValueType = Value;` For usage, both mean the same thing but are named differently. Refactoring of internal type alias should solve the problem.