"fold": a replacement for "reduce"

[Meta]

On Saturday, 29 March 2014 at 00:58:46 UTC, Meta wrote:
> I'm confused now. What exactly was it that you were saying 
> didn't make sense?

Ah, I see now. When I said "it's a bit unintuitive as to what 
works and what doesn't", I was talking about how unless you know 
exactly what can be assigned to an alias and enum, it seems 
unintuitive or even random as to what works, but there are 
actually sound logical underpinnings.