Python-style enumerate for Nemerle

So instead of just whining about Nemerle, here's a something potentially useful. I found I missed Python's built-in enumerate function. It wasn't too hard to implement in Nemerle:

public class Enumerator['a] : IEnumerable[(int * 'a)] {
    private e: IEnumerable['a];
    
    public this(e: IEnumerable['a]) {
        this.e = e;
    }
    
    public GetEnumerator(): IEnumerator[(int * 'a)] {
        mutable i = 0;
        foreach (elem in this.e) {
            yield (i, elem);
            i++;
        }
    }
}

Usage:

foreach ((index, item) in Enumerator(list)) {
    System.Console.WriteLine($"index for $item: $index");
}

The naming might not be optimal, with potential confusion with the standard libraries, but I don't care at the moment. Use and enjoy.