pub component Map<T, Y>(data list<T>) (res list<Y>) {
    nodes {
        handler IMapHandler,

        Iter<T>
        Map<T, Y>{handler}
        List<T>
    }

    :data -> iter -> map -> list -> :res
}

...

component Main(start) (stop) {
    nodes {
        Map{Decr<int>}
    }
    // ...
}