I was confused by that too. Under the "Types" page of the guide[1], they say: > Every value in Acton is of a certain data type, which tells Acton what kind of

I was confused by that too. Under the "Types" page of the guide[1], they say: > Every value in Acton is of a certain data type, which tells Acton what kind of data is being specified so it knows how to work with the data. Acton is a statically typed language, which means the type of all values must be known when we compile the program. Unlike many traditional languges like Java or C++, where types must be explicitly stated everywhere, we can write most Acton programs without types. The Acton compiler features a powerful type inferencer which will infer the types used in the program. > Acton implements the Hindley-Milner (HM) type system, which is common in languages with static types, like Haskell and Rust. Acton extends further from HM to support additional features. The language also has inheritance (and thus presumably subtyping), protocols (interfaces, I think), and generics. Historically, those features have not played nice with HM inference, so I'm not sure what's going on there. [1]: https://acton.guide/types/intro.html https://acton.guide/types/intro.html