I apologize... my question was unclear. It was not the standard MonadPlus class and functions that I was asking about, but the specific instance for Maybe (i.e. or_maybe). As it happens, a couple of times in the past couple of weeks, I might have used such a function if it were available in the standard libraries. (Thanks, anyway!) #g -- At 11:30 14/12/03 +0100, Tomasz Zielonka wrote:
On Fri, Dec 12, 2003 at 08:55:59PM +0000, Graham Klyne wrote:
At 14:17 12/12/03 -0500, Derek Elkins wrote:
This will also provide a migration path if you want a more featureful monad. (or_maybe is mplus, fail or mzero can be used for Nothing when you explicitly want to fail).
Is this or_maybe (and friends) actually defined in any of the standard libraries? (Google found only one hit, in an old IRC log.)
mplus and mzero are methods in class MonadPlus, which you'll found in module Monad. There is an instance of MonadPlus for Maybe.
Best regards, Tom
-- .signature: Too many levels of symbolic links
------------ Graham Klyne For email: http://www.ninebynine.org/#Contact