Variables

Brunost has two kinds of variable bindings: immutable (låst) and mutable (open). Prefer låst — mutability is opt-in.

Immutable variables — låst

låst name er "Astrid"
låst year er 1814

låst variables cannot be reassigned after declaration. Any attempt raises an ImmutableAssignment error at runtime.

låst x er 10
x er 20  // RuntimeError: ImmutableAssignment

Mutable variables — open

open counter er 0
counter er counter + 1
counter er counter + 1
// counter is now 2

Use open whenever you need to update a variable over time — loop counters, accumulators, etc.

The assignment operator — er

er serves two purposes depending on context:

Context	Meaning
Declaration (låst x er …)	Bind a name to a value
Statement (x er …)	Reassign a mutable variable
Expression (a erSameSom b)	Equality comparison (use erSameSom instead)

TIP

To test equality, use erSameSom, not er. Using er in an expression context assigns rather than compares.

Compound assignment operators

Mutable variables support shorthand update operators:

open score er 10
score += 5   // score is now 15
score -= 3   // score is now 12
score *= 2   // score is now 24
score /= 4   // score is now 6

These are equivalent to writing score er score + 5 etc., but shorter.

Scope

Variables follow lexical (block) scoping. A variable declared inside a block is not visible outside it:

bruk terminal

viss (sant) gjer {
  låst inner er "hello"
  terminal.skriv(inner)  // works
}
// terminal.skriv(inner)  // would fail — inner is out of scope

Functions create their own scope; they can read variables from enclosing scopes (closures).

Naming

Identifiers may contain letters (including æ, ø, å), digits, and underscores. They must not start with a digit.

låst gardsbruk er "Tømmerholt"
låst ål er 42