On 2008 Sep 14, at 10:01, Stephan Friedrichs wrote:
Johannes Waldmann wrote:
I think the crux of
the matter was that a monad is too general. Either there is a
result or
there is not. That's precisely the intended use of a Maybe.
Indeed "Monad m =>" is dangerous here
because not every Monad has a reasonable definition of "fail".
But that seems to be a problem in the (current) definition of
"Monad",
and its solution was "MonadZero", no?
I agree that the MonadZero class with a useful 'zero' :: m a would be
the right abstraction for views. But MonadZero is not part of base,
mtl
or any other common package, or am I missing something? Changing
this is
beyond a simple heap package ;)
MonadZero is what "fail" replaced in Haskell98. Many people consider
this a serious mistake.
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED]
system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED]
electrical and computer engineering, carnegie mellon university KF8NH
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