Extremely odd,
today ghc 6.4.2 (also on linux) works for me, too:
Prelude InfixR> show (A `And` A)
"A `And` A"
Prelude InfixR> show (And A A)
"A `And` A"
Prelude InfixR> read (show (And A A)) :: T
A `And` A
Prelude InfixR> read "And A A" :: T
*** Exception: Prelude.read: no parse
Prelude InfixR> r
[Moving to haskell-cafe]
Hi,
I want to know if it exists a null instruction (a instruction
that do anything
Not really, since instructions don't "do anything" anyway - they only
compute values.
If you are in the IO monad then "return ()" is the do nothing.
In the function world, "id" is the
Ian Lynagh wrote:
> ghci on 6.4.2 Linux works for me:
oops, works for me too - I forgot the type annotation when calling
read :) So it's fine in 6.4.2 - sorry for the disturbance then!
Cheers,
Misha
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Jason Dagit wrote:
> Before you get too caught up in deriving Read, remember that in
> Haskell it's very easy to create your own custom parser. Assuming you
> have previous experience with happy or parsec you could probably have
> already created a custom parser with time you've spent debugging t
Hello haskell-cafe,
i've added section
http://haskell.org/haskellwiki/OOP_vs_type_classes#Everything_is_object.3F
which lists cases when we DON'T use type classes to emulate
OOP classes features
--
Best regards,
Bulat mailto:[EMAIL PROTECTED]
__
On Sat, Aug 26, 2006 at 10:15:17PM +0300, Misha Aizatulin wrote:
> Neil Mitchell wrote:
> >> *Main> show $ A `And` A
> >> "A And A"
> >
> > For me, using GHCi 6.4.2 + Windows, I get:
> > "A `And` A"
>
> I installed GHC 6.4.2 now (on Linux). It really does print "A `And`
> A", but still doesn't
On 8/26/06, Misha Aizatulin <[EMAIL PROTECTED]> wrote:
Neil Mitchell wrote:
>> *Main> show $ A `And` A
>> "A And A"
>
> For me, using GHCi 6.4.2 + Windows, I get:
> "A `And` A"
I installed GHC 6.4.2 now (on Linux). It really does print "A `And`
A", but still doesn't read it. Would you agree th
Neil Mitchell wrote:
>> *Main> show $ A `And` A
>> "A And A"
>
> For me, using GHCi 6.4.2 + Windows, I get:
> "A `And` A"
I installed GHC 6.4.2 now (on Linux). It really does print "A `And`
A", but still doesn't read it. Would you agree that GHC doesn't conform
to the Haskell Report here? In fa
I like sigfpe's introduction to monads:
http://sigfpe.blogspot.com/2006/08/you-could-have-invented-monads-
and.html
-- Lennart
On Aug 26, 2006, at 14:04 , Andrea Rossato wrote:
Il Fri, Aug 25, 2006 at 01:13:58PM -0400, Cale Gibbard ebbe a
scrivere:
Hey cool, a new monad tutorial!
Il Fri, Aug 25, 2006 at 01:13:58PM -0400, Cale Gibbard ebbe a scrivere:
> Hey cool, a new monad tutorial! :)
>
> Just out of interest, have you seen my Monads as Containers article?
> http://www.haskell.org/haskellwiki/Monads_as_Containers
>
> Let me know what you think of it. I find that often n
Hello Andrea,
Saturday, August 26, 2006, 6:40:06 PM, you wrote:
>> Of course, newtype can also be used to define type whose only field
>> contains some function:
>>
>> newtype F = F (String->Int)
>>
>> Again, in this case language guarantees that internal F representation
>> will be the same as
[EMAIL PROTECTED] wrote:
> I found a way to remove this space leak, however, I do not really
> understand why there was a space leak in the first place. I would
> really appreciate any light that could be shed on this.
> instance ArrowChoice SF where
> left (SF f)
> = SF (\xs -> combine xs
Il Sat, Aug 26, 2006 at 06:00:02PM +0400, Bulat Ziganshin ebbe a scrivere:
> type HashFunction = (String->Int)
...
> createHash :: HashFunction -> IO Hash
> and
> createHash :: (String->Int) -> IO Hash
>
> are equivalent. So, technically speaking, you can't declare function
> types, there is only
Andrea Rossato wrote:
> this is what I'm trying to do, sort of: turn the code at the button
> into the do-notation.[1]
> type MSO a = State -> (a, State, Output)
>
> mkMSO :: a -> MSO a
> mkMSO a = \s -> (a, s, "")
>
> bindMSO :: MSO a -> (a -> MSO b) -> MSO b
> bindMSO m f = \x ->
>
Il Sat, Aug 26, 2006 at 02:25:51PM +0100, Brian Hulley ebbe a scrivere:
> runMSO :: MSO a -> State -> (a, State, Output)
> runMSO (MSO f) s = f s
this is exactly what I was looking for
runMSO (MSO f) s = f s
I've already done the previous part, but I was running it as:
runMSO a = evalMSO a 0
Hello Andrea,
Saturday, August 26, 2006, 1:44:19 PM, you wrote:
>> perhaps this is silly, but it is not possible to declare function
>> types?
>>
>> could you please indicate me some documentation that explains this
>> kind of stuff? So far I didn't find anything on that.
> well, I've found som
Andrea Rossato wrote:
this is what I'm trying to do, sort of: turn the code at the button
into the do-notation.[1]
module StateOutputMonad where
-- do notation only works with instances of Monad
import Control.Monad
data Term = Con Int
| Add Term Term
deriving (Show)
typ
Hello,
I have been using arrows to implement stream processors. At first, I
tried using the implementation presented in John Hughes' AFP arrows
lectures. However, this appeared to have a space leak in its
implementation of the left operator for ArrowChoice.
I found a way to remove this space lea
Il Sat, Aug 26, 2006 at 11:55:34AM +0100, Brian Hulley ebbe a scrivere:
> Yes, it's useful because it allows you to make a distinction between
> different uses of the same type of function and make these different uses
> into instances of different classes. It also allows you to hide the fact
>
Brian Hulley wrote:
I recommend chapter 8 of "Yet another Haskell Tutorial" which can be
downloaded from
http://www.haskell.org/haskellwiki/Books_and_tutorials#.E2.80.9CReal_world.E2.80.9D_tutorials
Sorry - the correct part of the wiki page is:
http://www.haskell.org/haskellwiki/Books_and_tuto
Andrea Rossato wrote:
Il Sat, Aug 26, 2006 at 01:27:38AM +0200, Daniel Fischer ebbe a
scrivere:
Because T a is a function type, namely Int -> (a,Int), so
...
iHowever, neither T1 a nor T2 a is a function type, a value of type
T1 a is a function _wrapped by the data (or value) constructor T1_
Il Sat, Aug 26, 2006 at 02:02:36AM +0200, Andrea Rossato ebbe a scrivere:
> perhaps this is silly, but it is not possible to declare function
> types?
>
> could you please indicate me some documentation that explains this
> kind of stuff? So far I didn't find anything on that.
well, I've found so
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