Why isn't there an instance Eq (a - b) ?
allValues :: (Bounded a,Enum a) = [a]
allValues = enumFrom minBound
instance (Bounded a,Enum a,Eq b) = Eq (a - b) where
p == q = fmap p allValues == fmap q allValues
Of course, it's not perfect, since empty types are finite but not
Bounded.
On 14 April 2010 16:03, Ashley Yakeley ash...@semantic.org wrote:
Why isn't there an instance Eq (a - b) ?
How do you prove that f = (2*) and g x = x + x are equal?
Mathematically, you can; but the only way you can prove it in
Haskell is by comparing the values for the entire domain (which gets
Consider the set of all rationals with 1 as a numerator, and positive
denominator, eg:
S = {1/n, n : Nat}
this is bounded, enumerable, but infinite. Which makes the whole
checking every value bit somewhat, shall we say, difficult. :)
So for instance, we want to show
f : S
On Wed, 2010-04-14 at 16:11 +1000, Ivan Miljenovic wrote:
but the only way you can prove it in
Haskell is by comparing the values for the entire domain (which gets
computationally expensive)...
It's not expensive if the domain is, for instance, Bool.
--
Ashley Yakeley
I guess nontermination is a problem (e.g. if one or both functions
fail to terminate for some values, equality will be undecidable).
/Jonas
On 14 April 2010 08:42, Ashley Yakeley ash...@semantic.org wrote:
On Wed, 2010-04-14 at 16:11 +1000, Ivan Miljenovic wrote:
but the only way you can prove
Joe Fredette wrote:
this is bounded, enumerable, but infinite.
The question is whether there are types like this. If so, we would need
a new class:
class Finite a where
allValues :: [a]
instance (Finite a,Eq b) = Eq (a - b) where
p == q = fmap p allValues == fmap q allValues
Your instances of Finite are not quite right:
bottom :: a
bottom = doSomethingToLoopInfinitely.
instance Finite () where
allValues = [(), bottom]
instance Finite Nothing where
allValues = [bottom]
Though at a guess an allValuesExculdingBottom function is also useful, perhaps
the class
Can anyone provide an example of an error that is prevented by this
warning? When exactly is it dangerous to ignore a monadic function's
return value?
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On Wed, 2010-04-14 at 08:13 +0100, Thomas Davie wrote:
Your instances of Finite are not quite right:
bottom :: a
bottom = doSomethingToLoopInfinitely.
instance Finite () where
allValues = [(), bottom]
Bottom is not a value, it's failure to evaluate to a value.
But if one did start
Hi all,
I was wondering if it's possible to have a class declaration that would
except both unlifted types and lifted types as instances.
For instance, I'm looking for something like
class Foo a b where
bar :: a - b
instance Foo Int Int where
bar = id
instance Foo Int#
Hi Phyx,
instance Foo Int# Int where
bar = iBox
What you want is not currently possible, for many of the same reasons
that you cannot instantiate polymorphic types (e.g. that of id) at
unboxed types. Because you can't then be polymorphic in the a in
Foo a b if a might be an unboxed type,
On Wed, Apr 14, 2010 at 2:32 AM, Ivan Miljenovic
ivan.miljeno...@gmail.com wrote:
Why not use Maybe for func1 in the first place? Or are you wanting to
automagically make all uses of head, tail, etc. safe?
In which case there is already the 'safe' package:
But if one did start considering bottom to be a value, one would have to
distinguish different ones. For instance, (error ABC) vs. (error
PQR). Obviously this is not finite.
Nor is it computable, since it must distinguish terminating programs
from nonterminating ones (i.e. the halting
Joe Fredette jfred...@gmail.com writes:
Consider the set of all rationals with 1 as a numerator, and positive
denominator, eg:
S = {1/n, n : Nat}
this is bounded, enumerable, but infinite.
Isn't making this an instance of Enum something of an abuse?
How would you use enumFromThenTo
On 14 Apr 2010, at 08:29, Ashley Yakeley wrote:
On Wed, 2010-04-14 at 08:13 +0100, Thomas Davie wrote:
Your instances of Finite are not quite right:
bottom :: a
bottom = doSomethingToLoopInfinitely.
instance Finite () where
allValues = [(), bottom]
Bottom is not a value, it's
On 14 Apr 2010, at 09:01, Jonas Almström Duregård wrote:
But if one did start considering bottom to be a value, one would have to
distinguish different ones. For instance, (error ABC) vs. (error
PQR). Obviously this is not finite.
Nor is it computable, since it must distinguish terminating
Ketil Malde wrote:
Another practical consideration is that checking a function taking a
simple Int parameter for equality would mean 2^65 function evaluations.
I think function equality would be too much of a black hole to be
worth it.
Oh FFS, _don't do that_.
--
Ashley Yakeley
f,g :: Bool - Int
f x = 6
g x = 6
We can in Haskell compute that these two functions are equal, without solving
the halting problem.
Of course, this is the nature of generally undecidable problems. They
are decidable in some cases, but not in general.
/Jonas
2010/4/14 Thomas Davie
f,g :: Bool - Int
f x = 6
g x = 6
We can in Haskell compute that these two functions are equal, without solving
the halting problem.
what about these?
f,g :: Bool - Int
f x = 6
g x = x `seq` 6
/Jonas
2010/4/14 Thomas Davie tom.da...@gmail.com:
On 14 Apr 2010, at 09:01, Jonas Almström
On 14 Apr 2010, at 09:08, Jonas Almström Duregård wrote:
f,g :: Bool - Int
f x = 6
g x = 6
We can in Haskell compute that these two functions are equal, without
solving the halting problem.
Of course, this is the nature of generally undecidable problems. They
are decidable in some
On 14 Apr 2010, at 09:12, Jonas Almström Duregård wrote:
f,g :: Bool - Int
f x = 6
g x = 6
We can in Haskell compute that these two functions are equal, without
solving the halting problem.
what about these?
f,g :: Bool - Int
f x = 6
g x = x `seq` 6
As pointed out on #haskell by
Thomas Davie wrote:
Certainly bottom is a value, and it's a value in *all* Haskell types.
This is a matter of interpretation. If you consider bottom to be a
value, then all the laws fail. For instance, (==) is supposed to be
reflexive, but undefined == undefined is not True for almost any
On Tue, 2010-04-13 at 23:03 -0700, Ashley Yakeley wrote:
Why isn't there an instance Eq (a - b) ?
allValues :: (Bounded a,Enum a) = [a]
allValues = enumFrom minBound
instance (Bounded a,Enum a,Eq b) = Eq (a - b) where
p == q = fmap p allValues == fmap q allValues
Of
On 14 Apr 2010, at 09:17, Ashley Yakeley wrote:
Thomas Davie wrote:
Certainly bottom is a value, and it's a value in *all* Haskell types.
This is a matter of interpretation. If you consider bottom to be a value,
then all the laws fail. For instance, (==) is supposed to be reflexive, but
Maciej Piechotka wrote:
I guess that the fact that:
- It is costly.
No, it's not. Evaluating equality for Bool - Int does not take
significantly longer than for its isomorph (Int,Int). The latter has
an Eq instance, so why doesn't the former?
--
Ashley Yakeley
On Wed, 2010-04-14 at 01:21 -0700, Ashley Yakeley wrote:
Maciej Piechotka wrote:
I guess that the fact that:
- It is costly.
No, it's not. Evaluating equality for Bool - Int does not take
significantly longer than for its isomorph (Int,Int). The latter has
an Eq instance, so why
Thomas Davie wrote:
Because we consider that the Functor laws must hold for all values in the type
(including bottom).
This is not so for IO, which is an instance of Functor. fmap id
undefined is not bottom.
--
Ashley Yakeley
___
Haskell-Cafe
On 14 Apr 2010, at 09:25, Ashley Yakeley wrote:
Thomas Davie wrote:
Because we consider that the Functor laws must hold for all values in the
type (including bottom).
This is not so for IO, which is an instance of Functor. fmap id undefined
is not bottom.
It isn't?
fPrelude fmap id
On Wed, 2010-04-14 at 09:29 +0100, Thomas Davie wrote:
It isn't?
fPrelude fmap id (undefined :: IO ())
*** Exception: Prelude.undefined
ghci is helpfully running the IO action for you. Try this:
seq (fmap id (undefined :: IO ())) not bottom
--
Ashley Yakeley
what about these?
f,g :: Bool - Int
f x = 6
g x = x `seq` 6
As pointed out on #haskell by roconnor, we apparently don't care, this is a
shame... We only care that x == y = f x == g y, and x == y can't tell if
_|_ == _|_.
So the facts that
(1) f == g
(2) f undefined = 6
(3) g undefined =
On 14 Apr 2010, at 09:31, Ashley Yakeley wrote:
On Wed, 2010-04-14 at 09:29 +0100, Thomas Davie wrote:
It isn't?
fPrelude fmap id (undefined :: IO ())
*** Exception: Prelude.undefined
ghci is helpfully running the IO action for you. Try this:
seq (fmap id (undefined :: IO ())) not
On 14 Apr 2010, at 09:35, Jonas Almström Duregård wrote:
what about these?
f,g :: Bool - Int
f x = 6
g x = x `seq` 6
As pointed out on #haskell by roconnor, we apparently don't care, this is a
shame... We only care that x == y = f x == g y, and x == y can't tell if
_|_ == _|_.
So
Thomas Davie wrote:
I guess this further reinforces my point though – we have a mixture of places
where we consider _|_ when considering laws, and places where we don't consider
_|_. This surely needs better defined somewhere.
It's easy: don't consider bottom as a value, and the laws work
On 14 Apr 2010, at 09:39, Ashley Yakeley wrote:
Thomas Davie wrote:
I guess this further reinforces my point though – we have a mixture of
places where we consider _|_ when considering laws, and places where we
don't consider _|_. This surely needs better defined somewhere.
It's easy:
Ashley Yakeley ash...@semantic.org writes:
Another practical consideration is that checking a function taking a
simple Int parameter for equality would mean 2^65 function evaluations.
I think function equality would be too much of a black hole to be
worth it.
Oh FFS, _don't do that_.
I
Oh well, thanks for all the response.
I have a module with lots of one line function definitons, and they just
*look* ugly when I wrap the return type with Maybe. This is a
straightforward, and trivial job (the conversion) and I really don't care
about other problems (such as non-termination plus
On 14 April 2010 03:48, Brent Yorgey byor...@seas.upenn.edu wrote:
Can someone more well-versed in the intricacies of type checking with
associated types explain this? Or is this a bug in GHC?
Hi Brent
Maybe you can't compose linear maps of the same type, and thus can't
build a valid monoid
Ketil Malde wrote:
(If you'd made clear from the start that when you say Enum a, Bounded a
you really mean Bool, you might have avoided these replies that you
apparently find offensive.)
I don't mean Bool. There are lots of small finite types, for instance,
(), Word8, Maybe Bool, and so on.
Ashley Yakeley ash...@semantic.org writes:
On Wed, 2010-04-14 at 16:11 +1000, Ivan Miljenovic wrote:
but the only way you can prove it in
Haskell is by comparing the values for the entire domain (which gets
computationally expensive)...
It's not expensive if the domain is, for instance,
Roel van Dijk vandijk.r...@gmail.com writes:
Can anyone provide an example of an error that is prevented by this
warning? When exactly is it dangerous to ignore a monadic function's
return value?
See Neil's original rationale in the bug report:
http://hackage.haskell.org/trac/ghc/ticket/3263
Jonas Almström Duregård wrote:
So the facts that
(1) f == g
(2) f undefined = 6
(3) g undefined = undefined
is not a problem?
This is not a problem. f and g represent the same moral function, they
are just implemented differently. f is smart enough to know that its
argument doesn't matter,
Ivan Lazar Miljenovic wrote:
Ashley Yakeley ash...@semantic.org writes:
On Wed, 2010-04-14 at 16:11 +1000, Ivan Miljenovic wrote:
but the only way you can prove it in
Haskell is by comparing the values for the entire domain (which gets
computationally expensive)...
It's not expensive if the
Cafe,
How can I provide a Data instance for a GADT? I am trying to TH on it, and
Uniplate requires Data.
I tried StandaloneDeriving, but it seems not to work.
Best,
--
Ozgur Akgun
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answering to myself: I guess this is related:
http://hackage.haskell.org/trac/ghc/ticket/3497
On 14 April 2010 10:13, Ozgur Akgun ozgurak...@gmail.com wrote:
Cafe,
How can I provide a Data instance for a GADT? I am trying to TH on it, and
Uniplate requires Data.
I tried StandaloneDeriving,
On 14/04/2010, at 09:05, Xiao-Yong Jin wrote:
I want to use 'mapM' on Data.Vector.Vector, but it looks
like the only 'mapM' defined is in
Data.Vector.Fusion.Stream.Monadic. I'm able to use 'stream'
and 'liftStream' to convert a 'Vector' to a monadic stream,
on which I can use 'mapM'. But I
Seeing this old thread[1], I hope something happened towards enabling this.
Does anybody know the current status about using TH on GADTs?
[1]
http://www.haskell.org/pipermail/template-haskell/2006-August/000567.html
On 14 April 2010 10:32, Ozgur Akgun ozgurak...@gmail.com wrote:
answering to
Bertram Felgenhauer wrote:
Yves Parès wrote:
I answered my own question by reading this monad-prompt example:
http://paste.lisp.org/display/53766
But one issue remains: those examples show how to make play EITHER a human
or an AI. I don't see how to make a human player and an AI play
I have now had a chance to experiment with these a bit, and have come up with
some changes that bring random-fu's speed in these tests into line with
Control.Monad.Random's when compiled with ghc-6.12.1, although it is still a
bit slower when using GHC 6.10.4. This is partially because one of
Ashley Yakeley schrieb:
Joe Fredette wrote:
this is bounded, enumerable, but infinite.
The question is whether there are types like this. If so, we would
need a new class:
I assume that comparing functions is more oftenly a mistake then
actually wanted. Say I have compared
f x == f y
and
On Wed, 14 Apr 2010, Ashley Yakeley wrote:
Joe Fredette wrote:
this is bounded, enumerable, but infinite.
The question is whether there are types like this. If so, we would need a new
class:
class Finite a where
allValues :: [a]
instance (Finite a,Eq b) = Eq (a - b) where
p == q
gladst...@gladstein.com writes:
I may need to put some #ifdef conditionalizations into some
cross-platform code. I'm wondering where I can find the definitions of
symbols like __NHC__. I tried googling but I'm swamped by uses, no
definitions that I can see.
Looks like they're here:
On Wed, Apr 14, 2010 at 4:41 AM, rocon...@theorem.ca wrote:
As ski noted on #haskell we probably want to extend this to work on Compact
types and not just Finite types
instance (Compact a, Eq b) = Eq (a - b) where ...
For example (Int - Bool) is a perfectly fine Compact set that isn't
Thanks very much Corey -- your suspicion is very well founded, and of course it
neatly explains the peculiar behaviour. It looks as if exec has obviously been
modified on RHEL and friends to refuse to execute anything in /tmp.
With a bit of luck I should be able to get cabal-install working
On Wed, Apr 14, 2010 at 5:13 AM, Luke Palmer lrpal...@gmail.com wrote:
On Wed, Apr 14, 2010 at 4:41 AM, rocon...@theorem.ca wrote:
As ski noted on #haskell we probably want to extend this to work on Compact
types and not just Finite types
instance (Compact a, Eq b) = Eq (a - b) where ...
On Wed, Apr 14, 2010 at 06:27:53AM -0500, Chris Dornan wrote:
Thanks very much Corey -- your suspicion is very well founded, and of course
it neatly explains the peculiar behaviour. It looks as if exec has obviously
been modified on RHEL and friends to refuse to execute anything in /tmp.
I
On Tue, Apr 13, 2010 at 9:59 PM, Max Cantor mxcan...@gmail.com wrote:
I'm in the camp of adding -fno-warn-unused-do-bind to my cabal files. I hate
sacrificing the purity of -Wall but I have so many forkIOs in my code that I
think it was the best option.
Max
I think a nice compromise
On Wed, Apr 14, 2010 at 09:51:52AM +0100, Stephen Tetley wrote:
On 14 April 2010 03:48, Brent Yorgey byor...@seas.upenn.edu wrote:
Can someone more well-versed in the intricacies of type checking with
associated types explain this? Or is this a bug in GHC?
If you take the definition of
Yves, that is exactly how I designed my program so far.
Human player needs a monad IO, AI needs just a monad, whatever it is, and I
make both run in IO.
And, as you said, the type of the ai (bot :: Monad m = Player m) contains
no IO, so I know that, even if I make it run in IO, it won't make any
On 15/04/2010, at 00:30, Brent Yorgey wrote:
On Wed, Apr 14, 2010 at 09:51:52AM +0100, Stephen Tetley wrote:
On 14 April 2010 03:48, Brent Yorgey byor...@seas.upenn.edu wrote:
Can someone more well-versed in the intricacies of type checking with
associated types explain this? Or is this a
On Wed, 14 Apr 2010 19:37:22 +1000, Roman Leshchinskiy wrote:
On 14/04/2010, at 09:05, Xiao-Yong Jin wrote:
I want to use 'mapM' on Data.Vector.Vector, but it looks
like the only 'mapM' defined is in
Data.Vector.Fusion.Stream.Monadic. I'm able to use 'stream'
and 'liftStream' to convert a
On Thu, Apr 15, 2010 at 12:48:20AM +1000, Roman Leshchinskiy wrote:
Right, this seems weird to me. Why is there still a 'u' mentioned in
the constraints? Actually, I don't even see why there ought to be
both v and v1. The type of (*.*) mentions three type variables, u, v, and
w:
__NHC__ is defined when the code is compiled with the nhc98 compiler
[1]. Similarly Hugs is another Haskell implementation.
[1]: http://www.haskell.org/nhc98/
On 14 April 2010 11:36, gladst...@gladstein.com wrote:
I may need to put some #ifdef conditionalizations into some
cross-platform
I have some difficulties to see the use of PromptT, because in the tutorial,
this type is never mentioned, and its operations (Return and :=) are
instead constructors of ProgramT...
Would you have some concrete examples? Because there I'm a bit lost (since
the tutorial doesn't match the
On Apr 14, 2010, at 07:27 , Chris Dornan wrote:
Thanks very much Corey -- your suspicion is very well founded, and
of course it neatly explains the peculiar behaviour. It looks as if
exec has obviously been modified on RHEL and friends to refuse to
execute anything in /tmp.
Unlikely that
Limestraël wrote:
I have some difficulties to see the use of PromptT, because in the tutorial,
this type is never mentioned, and its operations (Return and :=) are
instead constructors of ProgramT...
Would you have some concrete examples? Because there I'm a bit lost (since
the tutorial
Okay, I just understood that 'Prompt' was just a sort of view for 'Program'.
I'd like to make it very accessible, so please don't hesitate to report
any difficulties with finding and understanding documentation and examples!
Then I think the name 'Prompt' may be misleading for those who doesn't
Limestraël wrote:
Okay, I just understood that 'Prompt' was just a sort of view for 'Program'.
Right.
runMyStackT :: MyStackT (Player m) a - Player m a
According to what Bertram said, each strategy can pile its own custom monad
stack ON the (Player m) monad.
Yes, and I meant what
Okay, I start to understand better...
Just, Heinrich, how would implement the mapMonad function in terms of the
operational package?
You just shown the signature.
2010/4/14 Bertram Felgenhauer bertram.felgenha...@googlemail.com
Limestraėl wrote:
Okay, I just understood that 'Prompt' was just
On 2010-04-14 03:41, rocon...@theorem.ca wrote:
For example (Int - Bool) is a perfectly fine Compact set that isn't
finite
Did you mean Integer - Bool? Int - Bool is finite, but large.
--
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On Wed, 14 Apr 2010 09:15:04 -0500, Antoine Latter aslat...@gmail.com wrote:
On Tue, Apr 13, 2010 at 9:59 PM, Max Cantor mxcan...@gmail.com wrote:
I'm in the camp of adding -fno-warn-unused-do-bind to my cabal files. Â I
hate sacrificing the purity of -Wall but I have so many forkIOs in my
On Wed, Apr 14, 2010 at 02:07:52AM -0700, Ashley Yakeley wrote:
So the facts that
(1) f == g
(2) f undefined = 6
(3) g undefined = undefined
is not a problem?
This is not a problem. f and g represent the same moral function, they
are just implemented differently. f is smart enough to
Why isn't there an instance Eq (a - b) ?
I guess it's because even for those cases where it can be written, it
will rarely be what you want to do, so it's better to require the
programmer to explicitly request a function-comparison than to risk
silently using such a costly operation when the
Stefan Monnier monn...@iro.umontreal.ca wrote:
While we're here, I'd be more interested in a dirtyfast comparison
operation which could look like:
eq :: a - a - IO Bool
where the semantics is if (eq x y) returns True, then x and y are the
same object, else they may be different.
On Fri, Apr 09, 2010 at 09:07:29AM -0700, Bryan O'Sullivan wrote:
On Fri, Apr 9, 2010 at 6:44 AM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
As of 6.12.1, the new -fwarn-unused-do-bind warning is activated with
-Wall. This is based off a bug report by Neil Mitchell:
On Wed, Apr 14, 2010 at 2:22 PM, Stefan Monnier
monn...@iro.umontreal.ca wrote:
While we're here, I'd be more interested in a dirtyfast comparison
operation which could look like:
eq :: a - a - IO Bool
where the semantics is if (eq x y) returns True, then x and y are the
same object,
On Wed, 14 Apr 2010, Ashley Yakeley wrote:
On 2010-04-14 03:41, rocon...@theorem.ca wrote:
For example (Int - Bool) is a perfectly fine Compact set that isn't
finite
Did you mean Integer - Bool? Int - Bool is finite, but large.
Yes, I meant Integer - Bool.
--
Russell O'Connor
Hello Café,
do you know Nomic?
It's a fabulous and strange game where you have the right to change the
rules in the middle of the game!
In fact, changing the rules is the goal of the game. Changing a rule is
considered as a move.
Of course even that could be changed!
www.nomic.net
I'm wondering
On 2010-04-14 11:12, John Meacham wrote:
On Wed, Apr 14, 2010 at 02:07:52AM -0700, Ashley Yakeley wrote:
So the facts that
(1) f == g
(2) f undefined = 6
(3) g undefined = undefined
is not a problem?
This is not a problem. f and g represent the same moral function, they
are just implemented
On Apr 14, 2010, at 12:16 PM, Ashley Yakeley wrote:
They are distinct Haskell functions, but they represent the same
moral function.
If you're willing to accept that distinct functions can represent the
same moral function, you should be willing to accept that different
bottoms
A problem with GHC?
===
This post describes some odd behaviour I have seen in GHC 6.12.1 when writing
Combinatorrent. The post is literate Haskell so you can run it. The executive
summary: A space leak occurs when a new process is spawned from inside another
process - and I can't
On 2010-04-14 13:03, Alexander Solla wrote:
If you're willing to accept that distinct functions can represent the
same moral function, you should be willing to accept that different
bottoms represent the same moral value.
Bottoms should not be considered values. They are failures to calculate
On Apr 14, 2010, at 1:24 PM, Ashley Yakeley wrote:
Bottoms should not be considered values. They are failures to
calculate values, because your calculation would never terminate (or
similar condition).
And yet you are trying to recover the semantics of comparing bottoms.
On 2010-04-14 13:31, Alexander Solla wrote:
And yet you are trying to recover the semantics of comparing bottoms.
No, I don't think so.
--
Ashley Yakeley
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On Wed, 14 Apr 2010, Ashley Yakeley wrote:
On 2010-04-14 13:03, Alexander Solla wrote:
If you're willing to accept that distinct functions can represent the
same moral function, you should be willing to accept that different
bottoms represent the same moral value.
Bottoms should not be
Jesper Louis Andersen jesper.louis.ander...@gmail.com writes:
This post describes some odd behaviour I have seen in GHC 6.12.1 when writing
Combinatorrent. The post is literate Haskell so you can run it. The executive
summary: A space leak occurs when a new process is spawned from inside
On Wed, Apr 14, 2010 at 2:13 PM, Gregory Collins g...@gregorycollins.netwrote:
Jesper Louis Andersen jesper.louis.ander...@gmail.com writes:
This post describes some odd behaviour I have seen in GHC 6.12.1 when
writing
Combinatorrent. The post is literate Haskell so you can run it. The
On Wed, Apr 14, 2010 at 2:44 PM, Jason Dagit da...@codersbase.com wrote:
On Wed, Apr 14, 2010 at 2:13 PM, Gregory Collins
g...@gregorycollins.netwrote:
Jesper Louis Andersen jesper.louis.ander...@gmail.com writes:
This post describes some odd behaviour I have seen in GHC 6.12.1 when
On 2010-04-14 13:59, rocon...@theorem.ca wrote:
There is some notion of value, let's call it proper value, such that
bottom is not one.
In other words bottom is not a proper value.
Define a proper value to be a value x such that x == x.
So neither undefined nor (0.0/0.0) are proper values
Am Mittwoch 14 April 2010 23:13:13 schrieb Gregory Collins:
Jesper Louis Andersen jesper.louis.ander...@gmail.com writes:
This post describes some odd behaviour I have seen in GHC 6.12.1 when
writing Combinatorrent. The post is literate Haskell so you can run
it. The executive summary: A
Am Mittwoch 14 April 2010 23:49:43 schrieb Jason Dagit:
It will be interesting to hear what fixes this!
forever' m = do _ - m
forever' m
When I define that version of forever, the space leak goes away.
Not with optimisations.
Right: in this case /tmp is being mounted noexec.
Thanks again.
Chris
-Original Message-
From: Brandon S. Allbery KF8NH [mailto:allb...@ece.cmu.edu]
Sent: 14 April 2010 10:41 AM
To: Chris Dornan
Cc: Brandon S. Allbery KF8NH; 'Corey O'Connor'; Haskell-Cafe@haskell.org
Subject: Re:
On Wed, Apr 14, 2010 at 3:13 PM, Daniel Fischer daniel.is.fisc...@web.dewrote:
Am Mittwoch 14 April 2010 23:49:43 schrieb Jason Dagit:
It will be interesting to hear what fixes this!
forever' m = do _ - m
forever' m
When I define that version of forever, the
On Wed, Apr 14, 2010 at 09:14:18PM +0200, Dupont Corentin wrote:
Hello Café,
do you know Nomic?
It's a fabulous and strange game where you have the right to change the
rules in the middle of the game!
In fact, changing the rules is the goal of the game. Changing a rule is
considered as a
Am Donnerstag 15 April 2010 00:52:22 schrieb Jason Dagit:
The bad version, ghc --make NonTermination.hs:
\begin{code}
{-# OPTIONS -O2 #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- Note: Change the optimization to -O1 to get a terminating version
Doesn't seem to terminate with -O1 here
On Wed, Apr 14, 2010 at 04:43:20PM +0200, Limestraël wrote:
Yves, that is exactly how I designed my program so far.
Human player needs a monad IO, AI needs just a monad, whatever it is, and I
make both run in IO.
And, as you said, the type of the ai (bot :: Monad m = Player m) contains
no
On 2010-04-14 14:58, Ashley Yakeley wrote:
On 2010-04-14 13:59, rocon...@theorem.ca wrote:
There is some notion of value, let's call it proper value, such that
bottom is not one.
In other words bottom is not a proper value.
Define a proper value to be a value x such that x == x.
So neither
On Apr 14, 2010, at 19:24 , Brent Yorgey wrote:
On Wed, Apr 14, 2010 at 09:14:18PM +0200, Dupont Corentin wrote:
I'm wondering if it could be possible to implement a Nomic (or an
helper for
the game) in Haskell.
Haskell seems appropriate for that, since functions are first order
objects,
On Apr 14, 2010, at 5:10 PM, Ashley Yakeley wrote:
Worse, this rules out values of types that are not Eq.
In principle, every type is an instance of Eq, because every type
satisfies the identity function. Unfortunately, you can't DERIVE
instances in general. As you are finding out...
On Tue, Apr 13, 2010 at 3:47 AM, Erik de Castro Lopo
mle...@mega-nerd.commle%2...@mega-nerd.com
wrote:
Daniel Fischer wrote:
Am Dienstag 13 April 2010 09:29:18 schrieb Erik de Castro Lopo:
Anyone else have the same problem?
I have that problem with my hackage (Cabal/cabal-install)
On Wed, 2010-04-14 at 12:16 -0700, Ashley Yakeley wrote:
On 2010-04-14 11:12, John Meacham wrote:
On Wed, Apr 14, 2010 at 02:07:52AM -0700, Ashley Yakeley wrote:
So the facts that
(1) f == g
(2) f undefined = 6
(3) g undefined = undefined
is not a problem?
This is not a problem. f
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