Defines a struct.

defstruct is syntax sugar for defclass. It defines a class with all of the specified fields, along with:

• Implementations for the methods op-clone and op-eq?.
• A function bound to the global variable StructName:new, which instantiates the struct using positional arguments.
• A macro bound to the global variable StructName, which instantiates the struct using named arguments, similar to the tab macro.
• A function bound to the global variable StructName?, which tests whether or not a value is an instance of this struct.

To keep structs simple, their class clauses may only be const, met or prop. Classmacros, mixins, states, wrappers, field patterns and field initializers are not supported.

(defstruct Rect
  x y w h

  (met area ()
    (* @w @h)))

(let r (Rect:new 0 0 10 10))
(let s (Rect
  (x 2)
  (y 2)
  ..r))

(prn (.area s)) ; prints 100
(prn (Rect? s)) ; prints #t
(let t (clone s))
(prn (eq? s t) (same? s t)) ; prints #t #f