Records and Aggregate Constants

Related fields should travel under one name. A record declaration defines that shape and gives it a distinct type.

record Cell
    value as u16
    active as boolean
end

Field order is declaration order. Two record declarations with identical fields are still different types; Nucleus uses the declared record name rather than structural resemblance.

Static values

A record initializer supplies every field in order:

const defaultCell as Cell = (7, true)
var current as Cell = defaultCell

Arrays use square brackets and strings use string literals. Initializers are complete, type-directed descriptions of static storage. They do not call routines or run assignment statements before main.

An aggregate constant has an explicit aggregate type. Its direct named root is read-only, so defaultCell.value = 9 is rejected. It remains useful as a data source: code may read its fields, pass it to an aggregate parameter, return an alias to it or use it as an exact-type static initializer where supported.

The restriction is deliberately local to a source path rooted at the constant name. Nucleus has no transitive const type. If a constant is passed through an ordinary aggregate parameter, the alias does not retain a read-only marker. Portable code does not mutate such an alias: a ROM target may ignore the physical write, while a RAM-loaded target may change it.

Aggregate assignment

Assignment between two records or arrays copies the complete value only when their concrete types are identical. It does not rebind a parameter alias. Fields and nested elements remain available through ordinary paths such as table[index].value.

The companion reads one record constant, one array constant and one mutable record. It leaves observed equal to 22.

record Cell
    value as u16
    active as boolean
end

const defaultCell as Cell = (7, true)
const masks as u8[4] = [1, 2, 4, 8]
var current as Cell = defaultCell
var observed as u16 = 0

sub main()
    if current.active
        observed = current.value + defaultCell.value + u16(masks[3])
    end
end

Summary

• Records are nominal types with fields in declaration order.
• Static aggregate initializers are complete and type-directed.
• Aggregate constants own program-lifetime storage with a read-only direct root.
• Read-only status is not carried through ordinary aggregate aliases.
• Aggregate assignment requires exact concrete type identity.

See types, storage and declarations. The checked companion is 08-records.nu.