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Kalandra Documentation

Language reference

Records and enums

Model named data and alternatives with immutable values.

Use type for a named record with fields, and enum for a value that is one of several declared alternatives. Declarations are nominal: equal field layouts in unrelated declarations do not make them the same type.

Construct and update a record

kalandra
type Point:
  x: int
  y: int

fn main() -> int:
  original = Point { x: 2, y: 3 }
  moved = original with { x: 12 }
  original.x + moved.x + moved.y

This returns 17: original.x is 2, moved.x is 12 and moved.y is 3. Field initializer order follows source order. A with expression produces a new record; original remains unchanged. All required fields must be supplied once with compatible types. Records can contain supported Strings, collections, nested records or enums, and function values; the contained values are kept alive automatically. Copying a record preserves the backing aliases of its array fields. Use copy on an array field when the new record needs independent element storage.

Represent alternatives

kalandra
enum Reading:
  Missing
  Value:
    measurement: int

fn readOrDefault(reading: Reading) -> int:
  match reading:
    Reading.Missing: 0
    Reading.Value { measurement }: measurement

fn main() -> int:
  readOrDefault(Reading.Value { measurement: 42 })

This returns 42. Only the selected alternative exists as a language value. Read its payload by matching that variant. A final _ branch may handle remaining alternatives; missing, repeated and unreachable cases are diagnosed. Enum values do not gain record-style updates or implicit numeric ordinals.

Cross calls and workers

Records and enums keep their contained values alive automatically and can be passed through supported CPU worker tasks. Importing a declaration under a different name does not create a new type. GPU helpers can construct and pass local nonrecursive records/enums containing numeric/Bool scalars, numeric/Bool arrays and nested records. GPU task entry arguments and results cannot be records or enums; keep those values inside the placed helper.