Lykn

this and super

Surface Lykn has no this — Chapter 7 covered the rationale. But this and super exist in kernel code, and the reader needs to recognize them for JS interop.

this in Kernel Code

Inside a class body (which uses kernel syntax), this accesses instance properties via colon syntax:

(class Dog ()
  (constructor (name)
    (assign this:name name))

  (speak ()
    (console:log (template this:name " barks"))))

(bind d (new Dog "Rex"))
(d:speak)

class Dog {
  constructor(name) {
    this.name = name;
  }
  speak() {
    console.log(`${this.name} barks`);
  }
}
const d = new Dog("Rex");
d.speak();

this:name compiles to this.name. The colon syntax works the same way here as everywhere else — : becomes ..

super in Kernel Code

For class inheritance, super calls the parent constructor or parent methods:

(class Puppy (Dog)
  (constructor (name)
    (super name))

  (speak ()
    (super:speak)
    (console:log "...and wags tail")))

(super name) compiles to super(name). (super:speak) compiles to super.speak().

In Surface Code

If you need this for JS interop — calling a library that expects method-style invocation, working with a framework — use kernel passthrough (write the class in kernel forms) or js:bind. Chapter 14 (JS Interop) covers the full story.

In surface Lykn, the patterns that need this in JavaScript are handled with closures and explicit parameters. An object with methods that close over shared state is more explicit, more composable, and immune to binding confusion.