The Kernel Underneath
The surface has two function forms. The kernel has three, because JavaScript does:
| Surface | Kernel | JS output |
|---|---|---|
func | function | function name(...) { ... } |
fn | => | (...) => ... |
lambda | => | (...) => ... (same as fn) |
The Three Kernel Forms
;; Kernel vocabulary sketch. In surface files, kernel-only declaration
;; forms require explicit `kernel:` escape or a surface equivalent.
(function add (a b) (return (+ a b)))
(=> (x) (* x 2))
(lambda (x) (return (* x 2)))
function add(a, b) { return a + b; }
(x) => x * 2;
function(x) { return x * 2; }
The kernel’s function requires explicit return statements — just like JavaScript. The surface’s func handles return insertion automatically based on :returns.
Why You’d Use Kernel Forms
Rarely, in practice. func and fn provide type checking, and that’s usually what you want. But kernel forms are available for:
- JS interop where you need a specific function shape
- Inside
classbodies where methods use kernel syntax - Performance-critical code where you want to skip type checks without
--strip-assertions
The kernel forms are documented in the README’s form tables. The surface forms are what this book teaches.