Variables & Constants

let for values that change, const for values that shouldn't — and NEKOVA enforces the difference at runtime.

let

let name = "Ada"
let age = 30
name = "Grace"

let declares a variable. Reassigning it later — with or without writing let again — works fine.

const

const MAX_RETRIES = 3
show MAX_RETRIES

A const binding can be set once. Both reassigning it and redeclaring it raise a runtime error:

const MAX_RETRIES = 3
MAX_RETRIES = 5

error: Cannot reassign 'MAX_RETRIES' — it was declared with 'const' and
consts can't be changed after they're set.
  Use 'let MAX_RETRIES = ...' instead if you need it to change.

const is deliberately simpler than let — no destructuring form, no captured-think form. It exists for one job: a value that should never silently change.

Type hints

let age: int = 30
let name: str = "Ada"

Type hints are enforced when present. NEKOVA currently checks int, float, str, bool, list, and dict — a hint using any other word (like a descriptive number or text) is accepted syntactically but isn't type-checked, so stick to the six recognized names if you want real enforcement.

null

let user = null

if user:
    show "has a user"
else:
    show "no user"

null is falsy, compares equal to itself, and is distinct from false. Arithmetic on null raises a clear error rather than silently producing a wrong number:

show null + 1

error: Cannot use '+' between 'NoneType' and 'int'.

Booleans

let is_ready = true
let is_done = false

The type-mismatch guardrail

One specific case is worth calling out: mixing a string and a number with + raises instead of silently concatenating.

show "5" + 3

error: Cannot use '+' between 'str' and 'int'.
  Convert one side explicitly, e.g. str(value) or int(value).

This is deliberate — "5" + 3 silently becoming "53" is one of the most common sources of confusing bugs in JS-like languages, and NEKOVA's whole design philosophy is catching exactly this kind of mistake at the point it happens.