Bidirectional range dilemma

[Phil Lavoie]

On Sunday, 13 January 2013 at 16:31:30 UTC, Phil Lavoie wrote:
> Personally,
>
> I would have the policy implemented:
> permutations( Policy p = Policy.forward )() {
> ...
> }
>
> And maybe extend it with aliases:
>
> alias fPermutations permutations!( Policy.forward );
> alias rPermutations permutations!( Policy.backward );
> alias biPermutations permutations!( Policy.bidirectional );
>
> Cheers!

And of course I managed to invert alias terms again!