Lykn

Logical Operators

Lykn’s surface language provides three logical operators: and, or, and not. These compile to JavaScript’s &&, ||, and !.

Short-Circuit Evaluation

and and or are not merely boolean operators — they’re control flow. They evaluate their operands left to right and stop as soon as the result is determined:

and returns the first falsy value, or the last value if all are truthy:

(and user user:name)       ;; → user && user.name
;; If user is null, returns null (doesn't try user:name)

or returns the first truthy value, or the last value if all are falsy:

(bind name (or user-name "Anonymous"))
;; → const name = userName || "Anonymous"

not inverts truthiness:

(not active)               ;; → !active
(not (= x 0))             ;; → !(x === 0)

Variadic Logical Operators

Like arithmetic operators, and and or accept multiple arguments:

(and logged-in verified (not banned))
;; → loggedIn && verified && !banned

(or cached (fetch-from-db) (fetch-from-api) default-value)
;; → cached || fetchFromDb() || fetchFromApi() || defaultValue

Nullish Coalescing

?? provides a more precise alternative to or for default values. It triggers only on null or undefined — not on 0, "", or false:

(bind port (?? config-port 3000))
;; → const port = configPort ?? 3000

This matters when 0 or "" are valid values. (or config-port 3000) would replace a port of 0 with 3000. (?? config-port 3000) preserves 0 and only falls back for null/undefined.

Optional Chaining

JavaScript’s ?. operator (optional chaining) is not currently a surface form in Lykn. For nil-safe property access chains, use some-> (covered in Chapter 13):

(some-> user (get :address) (get :street))

This compiles to an IIFE with == null checks at each step, providing the same safety as ?. with more flexibility.