module SumsUp

To paraphrase Haskell's Data.Maybe docs:

Maybe represents an optional value. A Maybe value contains either a value (Maybe.just(1)), or is empty (Maybe.nothing).

0

hackage.haskell.org/package/base-4.14.0.0/docs/Data-Maybe.html

To parahprase Rust's std::result docs:

Result is a type used for returning and propagating errors. Result.success(value) represents a success and contains a value; Result.failure(error) represents an error with a propagated error.

0

doc.rust-lang.org/std/result/