Structs

Structs are named value types with typed fields. They are defined at the top level and can be used as variable types, parameter types, and return types.

Definition

struct Point {
    int x
    int y
}

Fields are separated by newlines (no semicolons inside struct bodies).

Instantiation

Point p = Point { x = 10, y = 20 };

With a different variable name:

Point origin = Point { x = 0, y = 0 };

Field access

print(p.x);   # 10
print(p.y);   # 20

Field mutation

p.x = 99;
print(p.x);   # 99

Nested structs

struct Rect {
    Point top_left
    Point bottom_right
}

main() {
    Rect r = Rect {
        top_left     = Point { x = 0, y = 10 },
        bottom_right = Point { x = 10, y = 0 }
    };
    print(r.top_left.y);       # 10
    print(r.bottom_right.x);   # 10
}

Structs in functions

Structs can be passed to and returned from functions:

Point translate(Point p, int dx, int dy) {
    return Point { x = p.x + dx, y = p.y + dy };
}

main() {
    Point p = Point { x = 1, y = 1 };
    Point q = translate(p, 5, 3);
    print(q.x);   # 6
    print(q.y);   # 4
}

Structs are value types

Structs are copied on assignment and when passed to functions. Mutations inside a function do not affect the caller's copy.

Struct registration

All struct declarations are registered before execution begins, so structs can be referenced anywhere in the file regardless of declaration order.