John Wiegley <johnw@newartisans.com> writes:

> The main reason I'd like it to be zero cost is that, once the change is made,
> there will be zero users of it. All existing code uses a single list, and it
> will be some time before authors feel confident enough in breaking backwards
> compatibility to start using multiple lists.

`seq-map' could maybe have that feature though, without impacting
`mapcar'.

Nico