Efficient way to create/copy immutable struct instance with modified data

[Merlin Diavova via Digitalmars-d-learn]

Hi all,

I'm trying to figure out the most efficient way to create 
modified instances of immutable structs.

Currently, I'm doing the following:

```d
immutable struct Node {
        string label;
        Node parentNode;
        NetworkPort port;

        auto withLabel(string newLabel)
        {
                return Node(newLabel, this.parentNode, this.port);
        }

        auto withParentNode(Node newParentNode)
        {
                return Node(this.label, newParentNode, this.port);
        }

        auto withNetworkPort(NetworkPort newPort)
        {
                return Node(this.label, this.parentNode, newPort);
        }
}
```
Coming from a scripting language the above makes the most sense.
In D, this an efficient way to do it? Are there any best 
practices around this?

Thanks in advance

Merlin