7. Structs

Structs are product types with named fields. While creating structs, each field has either an explicit default value or an implicit one derived from its type.

7.1 Declaring structs

struct Config:
    host: String
    port: int
    verbose: bool
end

Field names (host, port, verbose) are in scope inside the struct declaration.
The right-hand side gives the type of the field

7.2 Constructing and using structs

c1 := Config{}                      // all fields take their default values
c2 := Config{host = "localhost", verbose = true}        // override some fields

c1.port = 3
c1.host = "foo"

When a visible value has the same name as a field, its field initializer may omit = value:

host := "localhost"
port := 8080
verbose := true

c2 := Config{host, port, verbose}
c3 := Config{host = "example.com", port, verbose}

Config{host, port, verbose} is exactly equivalent to Config{host = host, port = port, verbose = verbose}. These entries are always named, not positional: their order does not need to match the declaration order.

Struct values can be read and updated through their fields using the usual . syntax.

7.3 Uniform function calls

A function in the same module as a struct may be called through a struct value when its first parameter has an explicit annotation for that struct type:

func set_port(c: Config, port: int):
    c.port = port
end

c1.set_port(8080) // shorthand for set_port(c1, 8080)

For an imported struct, the function is resolved in the module that defines the struct. This is just method-like syntactic sugar for an ordinary function call.

Recursive struct cycles must pass through Option[...]. For example, next: Option[Node] is valid, while next: Node and items: Vec[Node] are compile errors.

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