> Enumerations
- those are integers not enumerations.
In Golang they have a type Bool which is either true or false.
Can I define my own type using the same convention in GoLang? No. I can't. Ideally I want the ability to do this:
type Bool = Enum {
True
False
}
or
type Tri = Enum {
True
False
QuantumTrueFalseDuality
}
But in Golang I'm locked in with what the creators provided as primitive types. I can't go deeper. Rust you can.
> Sum types.
I don't think you know what a sum type is. This is what I mean by lack of knowledge. For sum type (A | B), A and B do not need to have a single thing in common and they do not need to share an interface. Think of a product type (A, B) as A and B and a sum type (A | B) as A or B.
The most glaring replacement of sum types in go are done with product types that contain errors from IO functions in GoLang. The Error type does not have anything in common with the Value it usually shadows and therefore both cannot be represented with an interface.
> Recursive types.
That's somewhat recursive. But that's a pointer. This works and is valid. Ideally though it shouldn't be a pointer but for efficiency during memory allocation this is a viable restriction. Recursive types only with pointer types.
> Parametric Polymorphism
I agree with you.
> Is this not acceptable?
No it is not acceptable. Interface is unusable until you make the type concrete with your asserts. Asserts are you executing a guess on a possible JSON permutation. In your second example you are guessing the type to be an array of INTs. What if that string was arriving over the wire as IO and you don't know what configuration it will be in? What if the typing was more complicated?
jsonString = "[1,2,True,[1,2,\"hello\"]]"
or
jsonString = randomJSONFromIO()
The assert also leaves an opening for a runtime error which is unacceptable.
imagine syntax like this:
type JSON :: []JSON | Struct{string: JSON} | bool | int | string | null
var x JSON = json.Unmarshal("[[1,2,True,[1,2,\"hello\"]],{}, null]")
JSON is a type represented using sums (|), products (Struct) and recursion (JSON). There is no possibility of run time errors here as you don't need to guess a specific permutation of JSON. You don't need to guess because such a type system can fully represent JSON. You see what is missing with go?