On Tue, Jan 6, 2009 at 11:23 PM, Tony Morris <[email protected]> wrote:
> No this is a mistake. Can is not an Option. Indeed it is (almost)
> impossible to write Can using Option (if you are familiar with Peano
> Arithmetic you will understand the need to qualify with almost).

While you're right in a (very) narrowly technical sense you're missing
the point that Lift's Can has functionality that is very closely
related to a combination of Option and Either in a touchy-feely
pragmatic getting-useful-things-actually-done sort of sense.

To prove the point, here,

  http://www.milessabin.com/misc/Chain.scala

is something I put together a while ago which can be used in a very
similar way to Can (at least, I expect that's the case ... I haven't
worked with Lift so I can't be sure) but which only exposes Option and
Either in it's public interface. It's also sufficiently Monad like to
get along nicely with for comprehensions.

Given the likelihood of confusion between Can and Option (irrespective
the algebraic niceties) I wish Lift had gone for something more like
that than a rename to Box.

Cheers,


Miles

-- 
Miles Sabin
tel:    +44 (0)1273 720 779
mobile: +44 (0)7813 944 528
skype:  milessabin

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