I actually think having different models (functional and imperative) just adds to confusion. I don't think immutability is all that useful personally, unless the language is purely functional to begin with. I'd keep it simple and stick to C as much as possible.

Why not go the other way and pass everything as a reference? After all that's what Java does, and that's how you'd pass any struct in C anyway. It's a rare case when I need to forbid the calling function to not modify an argument for whatever reason or because I don't trust it - in that case you can make a copy beforehand or use a const modifier. But in most cases I'd expect functions to modify the memory that I pass in, instead of allocating and returning new structures.

Why not have a simple `class` construct as in JavaScript? Keeping functions together in a class is very convenient and means you don't have to pass the struct as the first argument each time. That way `Array` can be a class, and would always be passed by reference. No ambiguity there, class instances are always mutable. Everyone is already familiar with it, it works.

A class method can simply map to a global C function: ``` ClassName_MethodName(*self, ...) ```

As an aside, using a syntax that people are already familiar with (and APIs!) would be great, and make something like this instantly usable. JavaScript has a fairly small core API which would be easy to emulate for example.