Adrian Neumann wrote:
data Tree a = Leaf a | Node a [Tree a]
But now the assignments require more than a simple top-down traversal.
For example: given a tree t and two nodes u,v, find the first common
ancestor.
Well, this problem doesn't make much sense in Haskell. How do you
specify
PR Stanley wrote:
data Tree = Leaf Int | Node Tree Int Tree
occurs :: Int - Tree - Bool
occurs m (Leaf n) = m == n
occurs m (Node l n r) = m == n || occurs m l || occurs m r
It works but I'd like to know if it can be improved in any way.
That's entirely fine.
The logical or || doesn't
I agree that (in this context, beginning learning Haskell) it is a
somewhat minor issue. But I disagree that this is something you should
ignore until it becomes a problem and I do think that it should be part
of learning Haskell. Properly using strictness is an important part of
using
That's a very good point. Yes, let's have some detailed explanations
accompanied by some good examples.
Cheers, Paul
At 08:43 03/12/2007, you wrote:
I agree that (in this context, beginning learning Haskell) it is a
somewhat minor issue. But I disagree that this is something you should
Stefan O'Rear wrote:
In my C programming, I've taken to using gdb as a REPL:
Ah, that's a nice trick, thanks!
I wish I there had been a gdb on MacOS 8.5 back then ;)
Regards,
apfelmus
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Hi,
2007/12/3, PR Stanley [EMAIL PROTECTED]:
Hi
Does the list consider
http://en.wikibooks.org/w/index.php?title=Haskell/Understanding_monadsoldid=933545
a reliable tutorial on monads and, if not, could you recommend an
onlien alternative please?
I really enjoyed All about Monads by Jeff
Hello PR,
Monday, December 3, 2007, 8:20:35 AM, you wrote:
occurs m (Node l n r) = m == n || occurs m l || occurs m r
in terms of style, i can prefer
occurs m (Node l n r) = or [m==n, occurs m l, occurs m r]
--
Best regards,
Bulatmailto:[EMAIL PROTECTED]
Hi
Does the list consider
http://en.wikibooks.org/w/index.php?title=Haskell/Understanding_monadsoldid=933545
a reliable tutorial on monads and, if not, could you recommend an
onlien alternative please?
Thanks,
Paul
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Johan Tibell [EMAIL PROTECTED] writes:
It would be great if someone could exemplify these rules of thumb,
e.g. Primitive types such as Int should be strict unless in the three
canonical examples X, Y and Z. My strictness radar is still quite
poor and I feel I can't make informed decisions on
ChrisK wrote:
For GHC 6.6 I created
foreign import ccall unsafe memcpy
memcpy :: MutableByteArray# RealWorld - MutableByteArray# RealWorld - Int#
- IO ()
{-# INLINE copySTU #-}
copySTU :: (Show i,Ix i,MArray (STUArray s) e (ST s)) = STUArray s i e -
STUArray s i e - ST s ()
s.clover:
Was this with tossing the partial sums code into the optimised bangs
program? Weird. I wonder if profiling will help explain why? In any case,
If nobody comes up with any other tweaks, I'll probably submit the
optimised bangs version to the shootout this weekend.
dons:
Strict in the elements, lazy in the spine:
data Tree = Leaf !Int | Node Tree !Int Tree
$ time ./A 25
49
./A 25 14.41s user 0.03s system 99% cpu 14.442 total
^^
3056K heap use.
And, finally, we can get a
http://hpaste.org/4151#a1
It is interesting, that the naive implementation
import Data.List (tails)
neighbours :: Int - [a] - [[a]]
neighbours w = rotL . take w . map (take 3) . tails . cycle
rotL :: [a] - [a]
rotL xs = last xs : init xs
type Rule a = [a] - a
step :: Int - Rule a - [a]
Thomas Davie wrote:
apfelmus wrote
Well, this problem doesn't make much sense in Haskell.
How do you specify the subtrees u and v in the first place?
One could alway store a node's depth at each node -- then you must
search for u and v, creating a list of what nodes you found at each
One could alway store a node's depth at each node -- then you must
search for u and v, creating a list of what nodes you found at each
depth, and finally, simply compare the lists -- O(n) in the depth of u
and v.
Bob
On 3 Dec 2007, at 08:40, apfelmus wrote:
Adrian Neumann wrote:
data
Hi
I've probably asked about the do construct, if that's the right
label. Unfortunately I'm still not quite sure of its role and more
specifically its syntax. Something to do with generators perhaps? A
description plus some examples would be most gratefully received.
Thanks, Paul
On Fri, Nov 02, 2007 at 01:30:44PM -0700, Greg Fitzgerald wrote:
Anybody know of an ARM back end for any of the Haskell compilers?
jhc can compile to the arm as well. This was tested by compiling a
simple program for the iPhone. :)
John
--
John Meacham - ⑆repetae.net⑆john⑈
2007/12/3, Albert Lee [EMAIL PROTECTED]:
I have been confussed by monad for a long time. and I can't stand for
it any more. so I start to translate the tutorial All About Monads
to my mother language Chinese.
My English is not good enough, so this work is only for my own study~
I know there
I have been confussed by monad for a long time. and I can't stand for
it any more. so I start to translate the tutorial All About Monads
to my mother language Chinese.
My English is not good enough, so this work is only for my own study~
I know there are some other Chinese fellow in this list,
What is wrong here? ghci tries (and fails) to deduce certain types for
the comp functions that I did not expect.
|type Block = [Command]
data Command = Skip | Assign String IntE | Cond BoolE Block Block |
Loop BoolE Block
data IntE= IntE Int | Var String | Sub IntE IntE |
Simon Peyton-Jones wrote:
| There may well have been changes to the strictness analyser that make
| some of the bangs (or most) unnecessary now. Also, its very likely
| I didn't check all combinations of strict and lazy arguments for the
| optimal evaluation strategy :)
|
| If it seems to be
Brad Clow wrote:
On Nov 28, 2007 11:30 AM, Matthew Brecknell [EMAIL PROTECTED] wrote:
Even with threads, results are evaluated only when they are needed (or
when forced by a strictness annotation). So the thread that needs a
result (or forces it) first will be the one to evaluate it.
So does
On Dec 3, 2007 6:55 AM, PR Stanley [EMAIL PROTECTED] wrote:
Hi
I've probably asked about the do construct, if that's the right
label. Unfortunately I'm still not quite sure of its role and more
specifically its syntax. Something to do with generators perhaps? A
description plus some examples
Reinier Lamers wrote:
ChrisK wrote:
For GHC 6.6 I created
foreign import ccall unsafe memcpy
memcpy :: MutableByteArray# RealWorld - MutableByteArray#
RealWorld - Int# - IO ()
{-# INLINE copySTU #-}
copySTU :: (Show i,Ix i,MArray (STUArray s) e (ST s)) = STUArray s i
e -
Adrian Neumann wrote:
data Tree a = Leaf a | Node a [Tree a]
example: given a tree t and two nodes u,v, find the
first common ancestor. In Java this is really simple,
because each node has a parent reference...
In Haskell however the best way I've come up with so
far is doing a BFS and
Andrew Coppin wrote:
ChrisK wrote:
For GHC 6.6 I created
foreign import ccall unsafe memcpy
memcpy :: MutableByteArray# RealWorld - MutableByteArray#
RealWorld - Int# - IO ()
{-# INLINE copySTU #-}
copySTU :: (Show i,Ix i,MArray (STUArray s) e (ST s)) = STUArray s i
e -
Adrian Neumann:
data Tree a = Leaf a | Node a [Tree a]
example: given a tree t and two nodes u,v, find the
first common ancestor.
The following solves what I think is a generalisation of this problem.
That is, given a tree and a predicate on its elements, return the
smallest subtree
On Nov 2, 2007 10:19 PM, nornagon [EMAIL PROTECTED] wrote:
On 03/11/2007, Greg Fitzgerald [EMAIL PROTECTED] wrote:
Anybody know of an ARM back end for any of the Haskell compilers?
If there's an arm-eabi port somewhere, I might be able to get Haskell
code running on the Nintendo DS...
Hi,
Some of the nofib suite are messed up by Yhc/nhc because of the
monomorphism restriction. Take imaginary/bernouilli as an example:
powers = [2..] : map (zipWith (*) (head powers)) powers
Hugs and GHC both see powers :: [[Integer]] and a CAF.
Yhc (and nhc) both see powers :: (Enum a, Num a)
Hi! I'm a begginer in haskell and I have a problem with an exercise, I expect
someone could help me:
In one hand I have a declaration of an algebra data, like this:
data AlgExp a = AlgExp
{ litI :: Int - a,
litB :: Bool - a,
add :: a - a - a,
and :: a - a - a,
ifte :: a - a - a -
On Mon, 2007-12-03 at 16:56 +0200, Yitzchak Gale wrote:
Adrian Neumann wrote:
data Tree a = Leaf a | Node a [Tree a]
example: given a tree t and two nodes u,v, find the
first common ancestor. In Java this is really simple,
because each node has a parent reference...
In Haskell however
On Mon, 2007-12-03 at 10:48 +0100, Ketil Malde wrote:
Johan Tibell [EMAIL PROTECTED] writes:
It would be great if someone could exemplify these rules of thumb,
e.g. Primitive types such as Int should be strict unless in the three
canonical examples X, Y and Z. My strictness radar is still
Carlo Vivari wrote:
data AlgExp a = AlgExp
{ litI :: Int - a,
litB :: Bool - a,
add :: a - a - a,
and :: a - a - a,
ifte :: a - a - a - a}
You're confusing sum and product types. That is, you're using a product type,
but you probably need a sum type, like this:
data Exp1 =
By all means apply a patch, I think.
Simon
| -Original Message-
| From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Neil Mitchell
| Sent: 03 December 2007 17:34
| To: Haskell Cafe
| Cc: Simon Marlow; Malcolm Wallace; Duncan Coutts
| Subject: [Haskell-cafe] Nofib
On 12/2/07, Steven Fodstad [EMAIL PROTECTED] wrote:
Sorry for not responding earlier. The haskell-cafe list is hard to keep
up with.
The process of finding geographic (lat/long) coordinates from a text
address is called geocoding. Obviously extracting the parts of an
address is part of
Probably one should understand how to use monads before worrying about
the do-notation. Here are some references:
I don't totally agree. You can teach monads to beginners just fine
using the do-notation. Unsuprisingly its very much like teaching
monads using bind. You describe a two line
Hello,
Atom is a language embedded in Haskell for describing reactive
software, primarily for realtime control applications. Based on
conditional term rewriting, an atom
description is composed of a set of state transition rules. The name
atom comes from the atomic behavior of rules: if a rule
Johan Tibell wrote:
It would be great if someone could exemplify these rules of thumb,
e.g. Primitive types such as Int should be strict unless in the three
canonical examples X, Y and Z. My strictness radar is still quite
poor and I feel I can't make informed decisions on when I need to make
Don Stewart wrote:
Please go ahead and submit. :) and remember to upload also to our wiki,
so we have a permanent record of the attempt,
http://haskell.org/haskellwiki/Shootout
Note down any ideas you have.
Now that GHC 6.6 is available, please you it?
Last time I looked at the
andrewcoppin:
Don Stewart wrote:
Please go ahead and submit. :) and remember to upload also to our wiki,
so we have a permanent record of the attempt,
http://haskell.org/haskellwiki/Shootout
Note down any ideas you have.
Now that GHC 6.6 is available, please you it?
Looks
Don Stewart wrote:
andrewcoppin:
Now that GHC 6.6 is available, please you it?
Looks like something broke in an edit. Feel free to correct it.
Oh well. ;-)
But then, the GHC wiki still says The 6.8 branch is the current STABLE,
and we are in the 6.8.1 release candidate phase.
On 03 Dec 2007, at 13:25 , Tim Newsham wrote:
Probably one should understand how to use monads before worrying
about
the do-notation. Here are some references:
I don't totally agree. You can teach monads to beginners just fine
using the do-notation. Unsuprisingly its very much like
This sounds like a really interesting piece of software. That being
another significant use for the name Atom these days is as an identifier
for a feed format.
http://en.wikipedia.org/wiki/Atom_(standard)
You may find it easier to advertise and romote this project with a more
unique name.
On Dec 3, 2007 1:09 PM, Denis Bueno [EMAIL PROTECTED] wrote:
I don't think I can conclude that there are *no* reasons to teach the
do-notation first. I just think that it is more instructive to teach
it later.
It's standard in mathematics teaching, when introducing a mathematical
structure
On 11/27/07, Matthew Brecknell [EMAIL PROTECTED] wrote:
wait_first :: [Wait a] - IO (a, [Wait a])
wait_first [] = error wait_first: nothing to wait for
wait_first ws = atomically (do_wait ws) where
do_wait [] = retry
do_wait (Wait w : ws) = do
r - readTVar w
case r of
Hi,
so today I built ghc-6.9.20071124.
First, make died because HsColour version = 1.8 was needed, couldn't
determine the version. I had HsColour 1.6, got myself 1.8, built and
installed.
make died again, same problem.
I added (v, Version) to the optionTable in HsColour.hs and it worked :)
Belatedly I realized that this answer should have been going to the list:
---
ChrisK wrote:
On Mittwoch, 28. November 2007, you wrote:
A safer gimmick...
Ben Franksen wrote:
tickWhileDoing :: String - IO a - IO a
tickWhileDoing msg act = do
hPutStr stderr msg hPutChar
G'day all.
On Mon, 2007-12-03 at 10:48 +0100, Ketil Malde wrote:
I find that I often need to add strictness when:
left thumb) parsing [Char] into something more compact, i.e. almost
all cases.
right thumb) storing data into maps, especially when the values
are produced by
PR Stanley wrote:
Does the list consider
http://en.wikibooks.org/w/index.php?title=Haskell/Understanding_monadsoldid=933545
a reliable tutorial on monads and, if not, could you recommend an
onlien alternative please?
I strongly recommend the original papers by Philip Wadler, especially this
To Nanonthief ..
VasiliIGalchin wrote:
.. however, I don't see in which file PATH can be set. Any help? I
really
want to get my Haskell build environment set up and cranking away.
Unless I misunderstood what you want, you can add a path to the PATH
variable by adding the line:
export
Dan Piponi wrote:
On Dec 3, 2007 1:09 PM, Denis Bueno [EMAIL PROTECTED] wrote:
I don't think I can conclude that there are *no* reasons to teach the
do-notation first. I just think that it is more instructive to teach
it later.
It's standard in mathematics teaching, when introducing a
foldExp :: AlgExp a - Exp - a
foldExp alg (LitI i) = litI alg i
foldExp alg (LitB i) = litB alg i
foldExp alg (add exp1 exp2) = ¿¿¿???
foldExp alg (and exp1 exp2) = ¿¿¿???
foldExp alg (ifte exp1 exp2 exp3) = ¿¿¿???
One comment: it looks like (add exp1 exp2), (and exp1 exp2) and so on
On Dec 3, 2007 9:23 PM, [EMAIL PROTECTED] wrote:
2. If it's logically a Functor, strictness will break the axioms,
so don't do that.
What do you mean by breaking the axioms? If I define
data List a = Nil | Cons !a !(List a)
instance Functor List where
fmap f Nil = Nil
fmap f (Cons x
On 12/3/07, Kalman Noel [EMAIL PROTECTED] wrote:
You're confusing sum and product types. That is, you're using a product
type,
but you probably need a sum type, like this:
I'm not so sure; it looks like they already have that type (Exp) and wants
to use AlgExp to hold the folding functions
On Dec 3, 2007 3:54 PM, Ben Franksen [EMAIL PROTECTED] wrote:
I don't buy this. As has been noted by others before, IO is a very special
case, in that it can't be defined in Haskell itself, and there is no
evaluation function runIO :: IO a - a.
I'm not sure what a function of type m a - a has
I've been playing with MonadPrompt for about ten days now, trying to get
it to do something useful for me.
Specifically, I'm trying to implement guess a number since that's the
hello world of haskell state programs, or so it seems to me. I want to
have this with scripting / replay / undo and
It took me forever to get comfortable with monads.
I think it helps if you've seen continuations, or done FP before, or a
variety of things that build familiarity.
But probably the only thing that I think will work for the masses of
plodders (there are always a few stars to crash the curve) is
On 3 Dec 2007, at 4:19 PM, Dan Piponi wrote:
On Dec 3, 2007 3:54 PM, Ben Franksen [EMAIL PROTECTED] wrote:
I don't buy this. As has been noted by others before, IO is a very
special
case, in that it can't be defined in Haskell itself, and there is no
evaluation function runIO :: IO a - a.
Hi everyone. With the permission of the authors, I'd like to announce the
release upload to Hackage of two games written in Haskell (you may've seen
them mentioned here once or twice before):
*Monadius
*Shu-thing
They are both scrolling 2 dimensional arcade shooting games which use 3D vector
Dan Piponi wrote:
On Dec 3, 2007 3:54 PM, Ben Franksen [EMAIL PROTECTED] wrote:
I don't buy this. As has been noted by others before, IO is a very
special case, in that it can't be defined in Haskell itself, and there is
no evaluation function runIO :: IO a - a.
I'm not sure what a
I am still in the early stages learning haskell, which is my first foray
into functional programming. Well there's no better way to learn than
to write something, so I started writing a game.
Mostly the thing looks good so far, far better than the C version did.
However, my problem is that
Ryan Ingram said:
Interesting, although this seems like a perfect use for orelse:
wait_stm :: Wait a - STM a
wait_stm (Wait w) = readTVar w = maybe retry return
wait :: Wait a - IO a
wait w = atomically $ wait_stm w
wait_first :: [Wait a] - IO (a, [Wait a])
wait_first [] = error
stefanor:
On Mon, Dec 03, 2007 at 08:47:48PM -0600, David McBride wrote:
I am still in the early stages learning haskell, which is my first foray
into functional programming. Well there's no better way to learn than to
write something, so I started writing a game.
Mostly the thing
On Mon, Dec 03, 2007 at 09:27:45PM -0600, Derek Elkins wrote:
On Mon, 2007-12-03 at 19:13 -0800, Stefan O'Rear wrote:
On Mon, Dec 03, 2007 at 09:18:18AM -0800, Carlo Vivari wrote:
Hi! I'm a begginer in haskell and I have a problem with an exercise, I
expect
someone could help me:
On Mon, Dec 03, 2007 at 09:18:18AM -0800, Carlo Vivari wrote:
Hi! I'm a begginer in haskell and I have a problem with an exercise, I expect
someone could help me:
In one hand I have a declaration of an algebra data, like this:
data AlgExp a = AlgExp
{ litI :: Int - a,
litB :: Bool
On Mon, Dec 03, 2007 at 08:47:48PM -0600, David McBride wrote:
I am still in the early stages learning haskell, which is my first foray
into functional programming. Well there's no better way to learn than to
write something, so I started writing a game.
Mostly the thing looks good so far,
On Mon, 2007-12-03 at 19:13 -0800, Stefan O'Rear wrote:
On Mon, Dec 03, 2007 at 09:18:18AM -0800, Carlo Vivari wrote:
Hi! I'm a begginer in haskell and I have a problem with an exercise, I
expect
someone could help me:
In one hand I have a declaration of an algebra data, like this:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer? If not, does
anyone have any recommendations for how to do it efficiently. There
are some obvious things that come to mind but which might involve
quite a bit of useless
On Dec 3, 2007, at 23:36 , Dan Piponi wrote:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer? If not, does
Isn't Integer unlimited (well, limited by RAM)?
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell]
Don's code intrigued me, so I fired up my trusty emacs and ghci, and
turned it into actual code, which type-checks. Well, ok, I kind of
randomly poked at it, while begging for help, which I received in
abundance from #haskell, particularly oerjan, and Don himself. Anyway,
here's the code:
{-#
On Mon, Dec 03, 2007 at 11:40:14PM -0500, Brandon S. Allbery KF8NH wrote:
On Dec 3, 2007, at 23:36 , Dan Piponi wrote:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer? If not, does
Isn't Integer unlimited (well,
dpiponi:
On Dec 3, 2007 9:10 PM, Don Stewart [EMAIL PROTECTED] wrote:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer?
Well, you could use testBit, which is pretty efficient,
But testBit tests only one bit at a
Actually, I suspect GHC's strictness analyzer will give you
reasonable performance with even the naive version, but fancier ideas
are at http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog
The problem with all those, however, is since they do bit-twiddling
and use shifts and
dpiponi:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer? If not, does
anyone have any recommendations for how to do it efficiently. There
are some obvious things that come to mind but which might involve
quite a bit
On Dec 3, 2007 6:36 PM, Ben Franksen [EMAIL PROTECTED] wrote:
then the special features of IO
will remain associated with monads in general, leading to a whole jumble of
completely wrong ideas about them.
As I only learnt about monads a couple of years ago, the process is
still fresh in my
On Dec 3, 2007 9:10 PM, Don Stewart [EMAIL PROTECTED] wrote:
Is there anything in any of the interfaces to Integer that will allow
me to quickly find the highest bit set in an Integer?
Well, you could use testBit, which is pretty efficient,
But testBit tests only one bit at a time. To prove
On Dec 3, 2007 9:32 PM, Sterling Clover [EMAIL PROTECTED] wrote:
if all else fails, be determined by unpacking it
into the primitives, which are (# Int#, ByteArr# #) with the Int# as
the number of limbs of the integer, as well as its sign.
That's the answer I'm looking for, thanks.
--
Dan
On 12/3/07, Dan Piponi [EMAIL PROTECTED] wrote:
On Dec 3, 2007 9:32 PM, Sterling Clover [EMAIL PROTECTED] wrote:
if all else fails, be determined by unpacking it
into the primitives, which are (# Int#, ByteArr# #) with the Int# as
the number of limbs of the integer, as well as its sign.
Hi
According to the Haskell Wikibook the is the
opposite of $. The text also oints out that the
| can be used as a substitute. I tried using
| but to no avail. Is the list au fait with the | operator?
Thanks,
Paul
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