ZoKrates/zokrates_cli/examples/structs/set_member.zok

struct Bar {
    field[2] c;
    bool d;
}

struct Foo {
    Bar a;
    bool b;
}

def main() -> Foo {
    Foo[2] mut f = [
        Foo {
            a: Bar {
                c: [0, 0],
                d: false
            },
            b: true
        },
        Foo {
            a: Bar {
                c: [0, 0],
                d: false
            },
            b: true
        }
    ];
    f[0].a.c = [42, 43];
    return f[0];
}