All of these didn't just give you something equivalent to C malloc()/free() with a parameter and result type. Maybe monads are useful in a lot of cases, but req

All of these didn't just give you something equivalent to C malloc()/free() with a parameter and result type. Maybe monads are useful in a lot of cases, but require a safe type system that prevents accidentally/negligently ignoring errors and language features to make it easy to unwrap the enum variants e.g. destructuring pattern matches and a collections of functions to work with them. I know both Rust and Haskell have those and suspect the other two examples as well. Without them they would be a pain in the ass to use.