A macro for algebraic data types (ADTs)

[glyh]

I just stumble across ADT in python, and it translate into this in hy. Which is kinda ugly.

Here I present a macro, so it's looks a bit better:

macro implementation

(defmacro defadt [name #* constructors]
  (let [alts []]
    `(do
       (import 
         __future__  [annotations]
         dataclasses [dataclass])
       ~@(lfor alt constructors 
            (if (= (type alt) hy.models.List)
              (let [[name #* fields] alt
                    fids (list (map 
                                (fn [id] (hy.models.Symbol f"arg{(+ id 1)}"))
                                (range (len fields))))]
                (alts.append name)
                `(defclass [dataclass] ~name []
                   ~@(lfor [f-id f-type] (list (zip fids fields))
                      `(annotate ~f-id ~f-type))
                   (defn __str__ [self]
                     (+ ~f"({name}" 
                        ~@(list 
                            (map (fn [fid] `(+ " " (str (getattr self ~(str fid))))) 
                                 fids)) 
                        ")"))))
              (do 
                (alts.append alt)
                `(defclass [dataclass] ~alt []
                   (defn __str__ [_]
                     ~f"({alt})")))))
       (setv ~name (| ~@alts)))))

(defadt Shape 
  [Point float float]
  [Circle float float float]
  [Rectangle float float float])

(Circle 3 4 5)

(defadt Tree
  Dead
  [Leaf int]
  [Branch Tree Tree])

(Branch
  (Branch (Leaf 1) (Leaf 2))
  (Branch (Dead) (Branch (Dead) (Dead))))

But noted that not all properties is supported, because in my perspective we should keep adt simple.

[glyh]

I don't know if there's a better syntax though, feel free to discuss, :)

One potential, conforming to hy's type annotation.

(defadt Shape
 [Point     #^float x
                    [y 0]]
 [Circle    #^float x
            #^float y
            #^float r]
 [Rectangle #^float x
                    y
            #^float w
            #^float h]
 [Whatever x y z a])

[Kodiologist]

Please don't use the issues list as a stream-of-consciousness. Think through what you want to say, experimenting as necessary, and then say it.

(I wrote this comment in reply to a lot of other comments that are now deleted.)

[glyh]

Well, I don't know what exactly should this macro look like because in genral lisps' don't have ADT. Therefore I don't know what the syntax should look like. I post the last one to ask people's opinion on it.

They do look a bit noisy, I'm going to clean it up a bit. Sorry about that.

EDIT: And potentially something here should be send to hy as an issue since I'm not sure if macros in hy is working properly again.