[PATCH] Refactor duplicate functions

[Tim Northover]

> I think the patch is good, if not pretty, so I'd like to commit. Can anyone
> comment on whether the tests are enough to guarantee preservation of the
> existing Darwin behaviour?

I think they looks reasonable. They cover the things I care about at
the moment anyway. I think you should go for it. (And very sorry for
the long delay in getting this committed. I know it wasn't exactly
your idea in the first place).

Cheers.

Tim.