[darcs-users] [patch185] add a witnessed zipper type (and 13 more)

[Ganesh Sittampalam]

Ganesh Sittampalam <ganesh at earth.li> added the comment:

On Sat, 20 Mar 2010, Jason Dagit wrote:

> Thanks!  This is a really cool patch set.  I've wanted a witnessed zipper
> for a long time!

BTW, this is only a list zipper, not a tree zipper, so it's not as cool as 
you might hope :-)

> One question (I don't have time right now to review the whole thing):
>
> +clowns :: FZipper a C(x y) -> Sealed ((RL a) C(x))
> +clowns (FZipper l _) = Sealed l
> +
> +jokers :: FZipper a C(x y) -> FlippedSeal (FL a) C(y)
> +jokers (FZipper _ r) = FlippedSeal r
>
> Why clowns and jokers?  It looks like it gives you either the left or right
> side of the zipper, but your terminology is not one I'm familiar with.  Is
> there a story behind the names?

google for "stuck in the middle with you lyrics" (or read the start of 
Conor McBride's paper)

Ganesh

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