Hasn't Ryan raised an interesting point, though?
Bottom is used to denote non-termination and run-time errors. Are they
the same thing? To me, they're not. A non-terminating program has
different behaviour from a failing program.
When it comes to strictness, the concept is defined in a
Taral wrote:
On 12/4/07, Simon Marlow [EMAIL PROTECTED] wrote:
do
x - newIVar
let y = readIVar x
writeIVar x 3
print y
(I wrote the let to better illustrate the problem, of course you can inline
y if you want). Now suppose the compiler decided to evaluate y before the
Jules Bean wrote:
Andrew Coppin wrote:
Andrew Coppin wrote:
copy :: Word32 - IOUArray Word32 Bool - Word32 - IO (IOUArray
Word32 Bool)
copy p grid size = do
let size' = size * p
grid' - newArray (1,size') False
mapM_
(\n - do
b - readArray grid n
if b
then mapM_ (\x -
Slides (in pdf) are now available online:
http://taichi.ddns.comp.nus.edu.sg/taichiwiki/SingHaskell2007
http://www.comp.nus.edu.sg/~sulzmann/singhaskell07/index.html
- Tom Martin
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Haskell-Cafe mailing list
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You usually don't need to worry about it. Just keep in mind that if you happen
to get a strange type error concerning an (overloaded) function *without type
signature*, it sometimes helps to add a signature.
/ Emil
On 2007-12-04 15:52, Rafael wrote:
I don't know about monomorphis
On Dec 5, 2007 12:16 AM, Aaron Denney [EMAIL PROTECTED] wrote:
we (the FPSIG group) defined:
data BTree a = Leaf a
| Branch (BTree a) a (BTree a)
Totally avoiding your question, but I'm curious as to why you
deliberately exclude empty trees.
Come to think of it, how can you
Roberto Zunino wrote:
Neil Mitchell wrote:
is there any automated
way to know when a function is strict in its arguments?
Yes, strictness analysis is a very well studied subject -
...and is undecidable, in general. ;-)
*thinks*
Conjecture #1: All nontrivial properties of
Galchin Vasili wrote:
http://code.enthought.com/enthon/ .. how do Haskell libraries/packages
stack up against this challenge?
I suspect this question is rather nontrivial to answer.
There's a library to do X. Well, yes, but is it any good? (Does it have
a nice API? Is it flexible? Is it
Hi Paolo,
On Dec 5, 2007 2:09 PM, Paulo J. Matos [EMAIL PROTECTED] wrote:
I'm glad that my initial post generated such an interesting discussion
but I'm still not understanding why the first version of findAllPath
seems to be computing the whole list even when I just request the
head, while
Tillmann Rendel wrote:
Andrew Coppin wrote:
*thinks*
Conjecture #1: All nontrivial properties of a computer program are
undecidable in general.
That is the well-known Rice's theorem.
Wait - Rice's *theorem*? So Rice *proved* this?
OMG, I was *right* about something! :-D
Conjecture #2:
I'm glad that my initial post generated such an interesting discussion
but I'm still not understanding why the first version of findAllPath
seems to be computing the whole list even when I just request the
head, while the second one doesn't. I thought that this was
denominated by findAllPath is
[EMAIL PROTECTED] wrote:
Hey everyone; recently I've been toying around with various methods of writing
a shell and reading the academic literature on such things. The best prior art
on the subject seems to be the ESTHER shell (see
http://citeseer.ist.psu.edu/689593.html,
Wow, thanks. I had a similar function (long if/then/else chain,
fromJust) that I haven't been happy with, but couldn't see how to
improve it. Now I have a much better idea for how to fix that
function.
Thanks again,
John Lato
the general pattern is : replace isNothing with a case match on
On Dec 5, 2007 5:40 PM, Paulo J. Matos [EMAIL PROTECTED] wrote:
Oh, but lfpaths is not nothing so that means that isNothing rtpaths
shouldn't be evaluated, right?
You're right, and I was stupid not to think about that case. Since
Luke already gave an in-depth analysis I'll be quiet now :-)
-
In an email to the HAppS listt today, alexj described that HAppS-State
provides a way to serialize function calls for replay either on-restart or
on other replicated boxes. (which actually helped me to understand somewhat
what's going on behind all its TemplateHaskell magic. This is somewhat more
On Dec 5, 2007 1:51 PM, Luke Palmer [EMAIL PROTECTED] wrote:
On Dec 4, 2007 9:41 PM, Paulo J. Matos [EMAIL PROTECTED] wrote:
Hello all,
As you might have possibly read in some previous blog posts:
http://users.ecs.soton.ac.uk/pocm06r/fpsig/?p=10
Hi,
Stefan and Isaac, thx for providing quick advice.
@Stefan: Unfortunately I have to use a list.
@Isaac: I do not get it. Could you please provide a short example of your
approach?
The question still remains. Which arguments do I have ghc to start with to
get the same behavior than hugs with
Steffen Mazanek wrote:
Hi,
Stefan and Isaac, thx for providing quick advice.
@Stefan: Unfortunately I have to use a list.
@Isaac: I do not get it. Could you please provide a short example of your
approach?
The question still remains. Which arguments do I have ghc to start with to
get the same
Hello,
i'm trying to wrap functions (a - b - ... - z) of any arity to functions
of type ([String] - y), where list of strings replaces the typed arguments.
one attempt looks like this (here written with type families, you can
replace it by functional dependencies or what ever):
type family Res
On Dec 5, 2007 1:43 PM, Benja Fallenstein [EMAIL PROTECTED] wrote:
Hi Paolo,
On Dec 5, 2007 2:09 PM, Paulo J. Matos [EMAIL PROTECTED] wrote:
I'm glad that my initial post generated such an interesting discussion
but I'm still not understanding why the first version of findAllPath
seems to
On Dec 5, 2007, at 16:00 , Philipp N. wrote:
the odd thing is. you can get this to work, if you have a
terminating type
as result type (for example (IO x)). then you can work with all
types (IO
x), (a - IO x), (a - b - IO x), ...
but i don't want this delimiter IO! any ideas?
Use ST
On Tuesday 04 December 2007 15:47:19 David Benbennick wrote:
On Dec 4, 2007 11:51 AM, Don Stewart [EMAIL PROTECTED] wrote:
Awesome. We can use this in Data.Bits, if you've got some QuickChecks
for it.
Hear hear. But is there any way to just make the compiler use
fastTestBit in place of
No, that doesn't work; it's close, but not quite. liftM doesn't have the
right type signature.
liftM :: Monad m = (a - r) - (m a1 - m r)
What would work is if you could define a function
liftLast :: Monad m = (a0 - a1 - ... - aN - r) - (a0 - a1 - ... -
aN - m r)
then
nary' f = runIdentity .
On 5 Dec 2007, [EMAIL PROTECTED] wrote:
Since from my Lisp days I know that code is data, it strikes me that
one could probably somehow smuggle Haskell expressions via this route
although I am not sure this is a good way to go or even how one would
do it (to turn, say, a list of the chosen
On Dec 5, 2007 11:56 AM, Andrew Coppin [EMAIL PROTECTED] wrote:
I was merely noting that questions of the form is X decidable? are
usually undecidable. (It's as if God himself wants to tease us...)
I take issue with your definition of usually then.
Whenever X is decidable is undecidable, 'X is
On Wed, 2007-12-05 at 10:01 +0100, Pablo Nogueira wrote:
Hasn't Ryan raised an interesting point, though?
Bottom is used to denote non-termination and run-time errors. Are they
the same thing?
Up to observational equality, yes.
To me, they're not. A non-terminating program has
different
On Dec 5, 2007, at 3:58 AM, Simon Marlow wrote:
Jan-Willem Maessen wrote:
Consider this:
do
x - newIVar
let y = readIVar x
writeIVar x 3
print y
(I wrote the let to better illustrate the problem, of course you
can inline y if you want). Now suppose the compiler decided to
On Dec 5, 2007 12:30 PM, Andrew Coppin [EMAIL PROTECTED] wrote:
Luke Palmer wrote:
On Dec 5, 2007 11:56 AM, Andrew Coppin [EMAIL PROTECTED] wrote:
I was merely noting that questions of the form is X decidable? are
usually undecidable. (It's as if God himself wants to tease us...)
I
Jan-Willem Maessen wrote:
Consider this:
do
x - newIVar
let y = readIVar x
writeIVar x 3
print y
(I wrote the let to better illustrate the problem, of course you can
inline y if you want). Now suppose the compiler decided to evaluate y
before the writeIVar. What's to prevent
Wouldn't any isomorphism do (like the Identity monad)? How about
nary' f = runIdentity . nary (liftM f) . return
Brandon S. Allbery KF8NH wrote:
On Dec 5, 2007, at 16:00 , Philipp N. wrote:
the odd thing is. you can get this to work, if you have a terminating
type
as result type (for
On Nov 29, 2007 5:31 AM, Reinier Lamers [EMAIL PROTECTED] wrote:
Especially in the fuzzy cases like this one, NLP often turns to machine
learning models. One could try to train a hidden Markov model or support
vector machines to label parts of the string as name, street,
number, city, etc.
Luke Palmer wrote:
On Dec 5, 2007 11:56 AM, Andrew Coppin [EMAIL PROTECTED] wrote:
I was merely noting that questions of the form is X decidable? are
usually undecidable. (It's as if God himself wants to tease us...)
I take issue with your definition of usually then.
Whenever X is
On Dec 3, 2007 7:43 AM, Peter Padawitz [EMAIL PROTECTED] wrote:
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
On Dec 5, 2007 11:44 AM, Jules Bean [EMAIL PROTECTED] wrote:
the general pattern is : replace isNothing with a case match on Nothing,
replace fromJust with a case match on Just, don't be afraid to case two
expressions at once.
That's a nice little insight. I'll remember that.
Paulo J. Matos wrote:
Hello all,
Hi.
findAllPath :: (a - Bool) - (BTree a) - Maybe [[a]]
findAllPath pred (Leaf l) | pred l = Just [[l]]
| otherwise = Nothing
findAllPath pred (Branch lf r rt) | pred r = let lfpaths = findAllPath pred lf
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Galchin Vasili
I believe that HUnit has absolutely not other package
dependencies. When I do a runhaskell Setup.hs build, I get
the following error message: gcc: installation problem, cannot
exec `cc1': No such file or
On Dec 4, 2007 10:00 PM, Neil Mitchell [EMAIL PROTECTED] wrote:
Hi
findAllPath :: (a - Bool) - (BTree a) - [[a]]
findAllPath pred = g where
g (Leaf l) | pred l = [[l]]
g (Branch lf r rt) | pred r = map (r:) $ (findAllPath pred
lf) ++ (findAllPath pred rt)
Brent Yorgey wrote:
Well, first of all, the definition of compCommand should use calls to
compBlock, not recursive calls to compCommand. But that's not the main
source of your problems.
What exactly are you trying to accomplish? And why do you need a type
class?
Whatever the code is
On Dec 5, 2007 10:38 PM, Ben Franksen [EMAIL PROTECTED] wrote:
data Command = Skip
class Java block command where
block_ :: [command] - block
compBlock :: [Command] - block
--compBlock = block_ . map compCommand
compCommand :: Command - command
My guess is that nothing's
Andrew Coppin wrote:
*thinks*
Conjecture #1: All nontrivial properties of a computer program are
undecidable in general.
That is the well-known Rice's theorem.
(A very handy one in exams about theoretical computer science, since you
can smash so many questions with follows from Rice).
On Dec 5, 2007 10:44 AM, Jules Bean [EMAIL PROTECTED] wrote:
Paulo J. Matos wrote:
Hello all,
Hi.
findAllPath :: (a - Bool) - (BTree a) - Maybe [[a]]
findAllPath pred (Leaf l) | pred l = Just [[l]]
| otherwise = Nothing
findAllPath pred (Branch lf r rt) |
On Dec 5, 2007 12:16 AM, Aaron Denney [EMAIL PROTECTED] wrote:
On 2007-12-04, Paulo J. Matos [EMAIL PROTECTED] wrote:
Hello all,
As you might have possibly read in some previous blog posts:
http://users.ecs.soton.ac.uk/pocm06r/fpsig/?p=10
http://users.ecs.soton.ac.uk/pocm06r/fpsig/?p=11
On 12/5/07, Ben Franksen [EMAIL PROTECTED] wrote:
data Command = Skip
class Java block command where
block_ :: [command] - block
compBlock :: [Command] - block
--compBlock = block_ . map compCommand
compCommand :: Command - command
This compiles ok. But when I ask ghci for the type of
I believe the exercise is about understanding folds.
There are two references that are related to the exercise:
A tutorial on the universality and expressiveness of fold, by Graham Hutton.
Dealing with large bananas, by Ralf Lammel, etc.
The last paper motivates well the need to gather all
On 06/12/2007, Tim Chevalier [EMAIL PROTECTED] wrote:
This is very well-trodden ground, but if you familiarize yourself with
the literature on the subject, then who knows, you may discover
something new. And you can take pleasure in knowing that you've
already independently conceived of an
This isn't strictly Haskell related, but anyway.
Next year I will be doing my honours in mathematics. One possible
topic for my thesis that I've thought of - and my supervisor is quite
enthused about - is to use graph theory to analyse various textual
sources, starting with source code but
On 12/5/07, Ivan Miljenovic [EMAIL PROTECTED] wrote:
How I envisage it happening is that a parser would be used to find all
functions in the given code, treat these as nodes in the graph and
then use directed edges to indicate which functions call other
functions.
aka a call graph. This is
See
http://doi.acm.org/10.1145/301631.301637
and
http://dx.doi.org/10.1016/S1571-0661(05)80288-9
Pablo Nogueira wrote:
Hasn't Ryan raised an interesting point, though?
Bottom is used to denote non-termination and run-time errors. Are they
the same thing? To me, they're not. A
Combinators get my code done, tralalalala, laughing out loud!
Quickcheck locates all of my bugs, tralalalala, laughing out loud!
Fusion laws make my code run fast, tralala, lalala, lololol!
Folks, I'm so done, Merry Christmas, tralalalala, laughing out loud!
On 2007.12.05 15:56:49 +0100, John van Groningen [EMAIL PROTECTED] scribbled
0.7K characters:
[EMAIL PROTECTED] wrote:
Hey everyone; recently I've been toying around with various methods of
writing a shell and reading the academic literature on such things. The best
prior art on the
hi
I have a matching problem... I am wanting to identify whether or not a string
is an opening substring of another (ignoring leading spaces). I have this:
word is a single word and str is a string.
match :: String - String - (Bool, String)match word str |
if removeSpace
Just remove that if. What comes after | is already a conditional.
Luke
On Dec 6, 2007 7:03 AM, Ryan Bloor [EMAIL PROTECTED] wrote:
hi
I have a matching problem... I am wanting to identify whether or not a
string is an opening substring of another (ignoring leading spaces). I have
this:
Oops, not quite. otherwise == should be otherwise =. Looks like
you already go this from the first one, but guard syntax looks like:
defn
| cond1 = ...
| cond2 = ...
| ...
| otherwise = ...
(otherwise is not actually necessary; it is just a synonym for True)
Luke
On Dec 6, 2007 7:09
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