Am Freitag, 10. Juli 2009 23:41 schrieben Sie:
On Jul 10, 2009, at 4:35 AM, Wolfgang Jeltsch wrote:
I fear that this instance doesn’t satisfy required laws. As far as
I know, the following equalities should hold:
(*) = ()
f * empty = empty
empty | g = g
This
Am Samstag, 11. Juli 2009 00:16 schrieben Sie:
On Friday 10 July 2009 4:35:15 am Wolfgang Jeltsch wrote:
I fear that this instance doesn’t satisfy required laws. As far as I
know, the following equalities should hold:
(*) = ()
f * empty = empty
IO already fails at this law,
On Fri, Jul 17, 2009 at 10:21 AM, Wolfgang
Jeltschg9ks1...@acme.softbase.org wrote:
Am Freitag, 10. Juli 2009 23:41 schrieben Sie:
Additionally, the second equality you provide is just wrong.
f * empty = empty is no more true than f * g = g,
I don’t understand this. The equation f * g = g
Am Donnerstag, 9. Juli 2009 15:27 schrieb Cristiano Paris:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y =
On Fri, Jul 10, 2009 at 10:35 AM, Wolfgang
Jeltschg9ks1...@acme.softbase.org wrote:
...
Hello Cristiano,
I fear that this instance doesn’t satisfy required laws. As far as I know, the
following equalities should hold:
(*) = ()
f * empty = empty
empty | g = g
This implies the
On Jul 10, 2009, at 4:35 AM, Wolfgang Jeltsch wrote:
I fear that this instance doesn’t satisfy required laws. As far as
I know, the
following equalities should hold:
(*) = ()
f * empty = empty
empty | g = g
This implies the following:
(f empty) | g = g
But this
On Friday 10 July 2009 4:35:15 am Wolfgang Jeltsch wrote:
I fear that this instance doesn’t satisfy required laws. As far as I know,
the following equalities should hold:
(*) = ()
f * empty = empty
IO already fails at this law, because (f * empty) is not the same as empty,
it is a
On Thu, 9 Jul 2009, Cristiano Paris wrote:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y = handle (\ (_ ::
On Thu, Jul 9, 2009 at 3:42 PM, Edward Kmett ekm...@gmail.com wrote:
Hrmm. This should probably be made consistent with the MonadPlus instance
for IO, so
empty = ioError (userError mzero)
I agree. Of course, that was only a first attempt :)
Cristiano
Hrmm. This should probably be made consistent with the MonadPlus instance
for IO, so
empty = ioError (userError mzero)
Otherwse, I'm surprised this isn't already in the standard library.
I'd suggest submitting it to librar...@.
-Edward Kmett
On Thu, Jul 9, 2009 at 9:27 AM, Cristiano Paris
To be honest -- that seems rather nice. Can has in Hackage?
Bob
On 9 Jul 2009, at 15:27, Cristiano Paris wrote:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance
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