2009/7/17 Andrew Coppin :
> I've been working hard this week, and I'm stumbled upon something which is
> probably of absolutely no surprise to anybody but me.
>
> Consider the following expression:
>
> (foo True, foo 'x')
>
> Is this expression well-typed?
>
> Astonishingly, the answer depends on
Why is there no Zippable class? There is.
You can use Data.Zippable from http://hackage.haskell.org/package/bff.
It gives you a function
tryZip :: Zippable k => k a -> k b -> Either String (k (a,b))
The Either in the return type is to capture an error message in case
the
two structures are
Why is there no Zippable class? There is.
You can use Data.Zippable from http://hackage.haskell.org/package/bff.
It gives you a function
tryZip :: Zippable k => k a -> k b -> Either String (k (a,b))
The Either in the return type is to capture an error message in case the
two structures are n
Yeah I tried applicative, but saw that the <*> operator didn't do what I
want with lists, and started looking elsewhere.
I didn't even see the ZipList! Actually the other problem is that the data
structure that I'm using won't support pure, so no Applicative :(
Though for a generic zip, Applicative
That would be great.
I can post some of my works on arduino , haskell and atom there.
Radamés
On Thu, Jul 16, 2009 at 23:54, Thomas
DuBuisson wrote:
> No, I'm not starting a new wiki (though it someone does or has then it
> should go on haskell.org, imo).
>
> Tom
>
> On Thu, Jul 16, 2009 at 7
No, I'm not starting a new wiki (though it someone does or has then it
should go on haskell.org, imo).
Tom
On Thu, Jul 16, 2009 at 7:38 PM, John Van Enk wrote:
> Are you starting a new Wiki? I'd absolutely love to have that resource.
>
> On Thu, Jul 16, 2009 at 8:14 PM, Thomas
> DuBuisson wrote:
Are you starting a new Wiki? I'd absolutely love to have that resource.
On Thu, Jul 16, 2009 at 8:14 PM, Thomas
DuBuisson wrote:
> The wiki [1] where Atom [2] once lived has been gone for some time
> now. The only resources I know for Atom are a couple blog posts, the
> haddock docs, and the Atom
A parser for JavaScript (admittedly a much simpler beast) is part of
Brown's WebBits:
http://hackage.haskell.org/packages/archive/WebBits/0.15/doc/html/
BrownPLT-JavaScript-Parser.html
Cheers,
Sterl.
On Jul 16, 2009, at 1:40 PM, Roy Lowrance wrote:
Turns out that Language.C uses alex and
Way cool. I have gained newfound respect for what I don't know. :)
Can there ever be more than one (observably different) valid definition
of pure for a given <*> that obeys all the laws? I would imagine that
there could be at most one.
Dan
Ryan Ingram wrote:
(I'm going to play fast and loo
(I'm going to play fast and loose with constructors for this post,
treating MyList and ZipList as if they were [])
On Thu, Jul 16, 2009 at 4:10 PM, Dan Weston wrote:
> -- different from [], sum rather than product
> instance Applicative MyList where
> pure x = x ::: Nil
> (<*>) (f ::: fs) (x :::
solved. see the haskell wiki for spoiler:
http://haskell.org/haskellwiki/Blow_your_mind
2009/7/16 Thomas Hartman :
> Is it possible to fix alternate' (the second version), or otherwise
> define a fast stepwise alternate that doesn't blow up on long lists?
>
> alternate just breaks up [1,2,3,4,5]
The wiki [1] where Atom [2] once lived has been gone for some time
now. The only resources I know for Atom are a couple blog posts, the
haddock docs, and the Atom source on patchtag. Is anyone aware of
other resources?
Tom
[1] http://funhdl.org/wiki/doku.php
[2] http://hackage.haskell.org/packa
Is it possible to fix alternate' (the second version), or otherwise
define a fast stepwise alternate that doesn't blow up on long lists?
alternate just breaks up [1,2,3,4,5] into ([1,3,5],[2,4])
Thanks!
{-# LANGUAGE BangPatterns #-}
import Data.List
import Control.Arrow
import Control.Parallel.S
On Thu, Jul 16, 2009 at 08:52:40PM +0100, Andrew Coppin wrote:
> Ross Mellgren wrote:
>> It's not where -- let also works
>>
>> Prelude> let { foo x = x } in (foo 1, foo True)
>> (1,True)
>
> Awesome. So by attempting to implement Haskell's type system, I have
> discovered that I actually don't u
After rereading page 2 of McBride and Paterson's Functional Pearl,
"Applicative programming with effects", I think you are just reinventing
Control.Applicative. The problem is that the default Applicative
instance for [] is wrong, being a direct product rather than a direct sum.
If [] were not
Is "everything" an acceptable answer?
-Ross
On Jul 16, 2009, at 6:38 PM, Derek Elkins wrote:
On Thu, Jul 16, 2009 at 2:52 PM, Andrew
Coppin wrote:
Ross Mellgren wrote:
It's not where -- let also works
Prelude> let { foo x = x } in (foo 1, foo True)
(1,True)
Awesome. So by attempting to i
I asked "why make life for regular Haskellers", and
On Jul 17, 2009, at 4:56 AM, Thomas Davie replied:
Because regular haskellers are perfectly capable of bookmarking http://haskell.org/usefullstuff.html
, while newbies will only get what google tells them -- the front
page.
Sorry, but
(1) I
On Thu, Jul 16, 2009 at 2:52 PM, Andrew
Coppin wrote:
> Ross Mellgren wrote:
>>
>> It's not where -- let also works
>>
>> Prelude> let { foo x = x } in (foo 1, foo True)
>> (1,True)
>
> Awesome. So by attempting to implement Haskell's type system, I have
> discovered that I actually don't understan
Beautiful. Can we have a version on hackage?
On Thu, Jul 16, 2009 at 5:56 PM, Job Vranish wrote:
> I was needing a way to zip generic data structures together today and was
> very annoyed to find that there is no Zippable class, or variant there of.
>
> So I made my own:
>
> class (Foldable f, Fu
I think there are some basic equivalents in the TypeCompose and
category-extras packages, for the record, but a standalone version
wouldn't hurt either!
- Jake
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I was needing a way to zip generic data structures together today and was
very annoyed to find that there is no Zippable class, or variant there of.
So I made my own:
class (Foldable f, Functor f) => Zippable f where
fmaps :: (Foldable g) => g (a -> b) -> f a -> f b
fmaps' :: [a -> b] -> f a
2009/7/16 Szekeres István :
> class ListUpdater a where
> updateFn :: Char -> Char
> update :: a -> a
>
> so I can define the update function for the different types of lists:
>
> instance ListUpdater String where
> update = map updateFn
>
> instance ListUpdater L.ByteString where
>
Hi,
I want to build a framework to apply different functions to different types
of lists and I want to generalize the solution as much as possible but my
Haskell knowledge is not really enough to do this (I'm a haskell novice).
The problem has two dimensions:
1. Lets say I have two functions:
r
Andrew Coppin wrote:
Awesome. So by attempting to implement Haskell's type system, I have
discovered that I actually don't understand Haskell's type system.
Who'd have thought it?
Clearly I must go consult the Report and check precisely what the
rules are...
I just read section 4.5 of the H
2009/7/16 Daniel van den Eijkel :
> In an ideal world, Haskell would be a perfect first programming language.
>
> But consider: If someone without any programming background learns Haskell
> as first language, she or he might have big problems using any other
> language after that. Unlearning what
dvde:
> In an ideal world, Haskell would be a perfect first programming language.
>
> But consider: If someone without any programming background learns
> Haskell as first language, she or he might have big problems using any
> other language after that. Unlearning what you can do with Haskell
> On Thu, Jul 16, 2009 at 8:22 PM, Thomas Hartman wrote:
>> Is this being worked on?
On Thu, Jul 16, 2009 at 12:35 PM, Bas van Dijk wrote:
> I have no idea.
Yes.
Bolingbroke, Peyton-Jones. "Types are calling conventions"
http://lambda-the-ultimate.org/node/3319
-- ryan
__
Ross Mellgren wrote:
It's not where -- let also works
Prelude> let { foo x = x } in (foo 1, foo True)
(1,True)
Awesome. So by attempting to implement Haskell's type system, I have
discovered that I actually don't understand Haskell's type system. Who'd
have thought it?
Clearly I must go co
On Thu, Jul 16, 2009 at 12:40 PM, Andrew Coppin wrote:
> Robert Greayer wrote:
>
>> f0 _ = (foo True, foo 'x') where foo = id
>>
>> is well-typed.
>>
>>
>
> Really? That actually works? How interesting... This suggests to me that
> where-clauses also do strange things to the type system.
You co
It's not where -- let also works
let { foo Prelude> let { foo x = x } in (foo 1, foo True)
(1,True)
Can you send the code you're trying that doesn't work?
-Ross
On Jul 16, 2009, at 3:40 PM, Andrew Coppin wrote:
Robert Greayer wrote:
f0 _ = (foo True, foo 'x') where foo = id
is well-typed.
In an ideal world, Haskell would be a perfect first programming language.
But consider: If someone without any programming background learns
Haskell as first language, she or he might have big problems using any
other language after that. Unlearning what you can do with Haskell is
much harder
Robert Greayer wrote:
f0 _ = (foo True, foo 'x') where foo = id
is well-typed.
Really? That actually works? How interesting... This suggests to me that
where-clauses also do strange things to the type system.
whereas
f1 foo = (foo True, foo 'x')
requires 'foo' to be polymorphic in its
On Thu, Jul 16, 2009 at 8:22 PM, Thomas Hartman wrote:
> I played with this a bit, and ok, it seems the difference between
> iterate' and iterate'' is
>
> h _ = 2
>
> tit' = head . drop 1 . iterate' h $ undefined
> tit'' = head . drop 1 . iterate'' h $ undefined
Exactly, iterate' first evaluates '
On Thu, Jul 16, 2009 at 7:45 PM, Thomas Hartman wrote:
> the strict functions seem very nice, will they eventually make their way into
> http://hackage.haskell.org/packages/archive/Stream/0.3.2/doc/html/Data-Stream.html
Note that there are two stream packages:
* 'Stream' by Wouter Swierstra (incl
On Thu, Jul 16, 2009 at 2:34 PM, Andrew
Coppin wrote:
> I've been working hard this week, and I'm stumbled upon something which is
> probably of absolutely no surprise to anybody but me.
>
> Consider the following expression:
>
> (foo True, foo 'x')
>
> Is this expression well-typed?
>
> Astonishi
Consider the following expression:
(foo True, foo 'x')
Is this expression well-typed?
Astonishingly, the answer depends on where "foo" is defined. If
"foo" is a local variable, then the above expression is guaranteed
to be ill-typed. However, if we have (for example)
That's not true:
mai
I believe that from Scheme to Haskell is a natural transition, as I
made the same transition myself. If you grasp the fundamental concepts
of Scheme, Haskell seems like a step up. I will describe Haskell in
terms of Scheme:
# Haskell programs are more correct from the ground up
Scheme will let yo
I've been working hard this week, and I'm stumbled upon something which
is probably of absolutely no surprise to anybody but me.
Consider the following expression:
(foo True, foo 'x')
Is this expression well-typed?
Astonishingly, the answer depends on where "foo" is defined. If "foo" is
a l
I played with this a bit, and ok, it seems the difference between
iterate' and iterate'' is
h _ = 2
tit' = head . drop 1 . iterate' h $ undefined
tit'' = head . drop 1 . iterate'' h $ undefined
> (Bas wishes for a type system that can express the different
strictness properties of these functio
the strict functions seem very nice, will they eventually make their way into
http://hackage.haskell.org/packages/archive/Stream/0.3.2/doc/html/Data-Stream.html
?
where is Control.Monad.StreamT? couldn't find it.
2009/7/15 Bas van Dijk :
> On Wed, Jul 15, 2009 at 3:02 AM, Thomas Hartman wrote:
Turns out that Language.C uses alex and happy.
I'm looking to use Parsec.
So back to the original question: Does anyone know of a C or java
parser written using Parsec?
- Roy
On Thu, Jul 16, 2009 at 12:43 PM, Roy Lowrance wrote:
> Thanks Rick. A perfect tip! - Roy
>
> On Thu, Jul 16, 2009 at 12
On 15 Jul 2009, at 06:03, Richard O'Keefe wrote:
On Jul 10, 2009, at 6:14 PM, Thomas Davie wrote:
In my mind, the front page is for nothing more than enticing people
to use Haskell for long enough to look at a second page where all
the useful stuff is if you are a haskell programmer.
I w
Thanks Rick. A perfect tip! - Roy
On Thu, Jul 16, 2009 at 12:29 PM, Rick R wrote:
> There is language.c
>
> http://www.sivity.net/projects/language.c/
> http://hackage.haskell.org/package/language-c
>
>
> From a parsing standpoint, C++ is a massive departure from C. Good luck
> though.
>
>
> On Th
I too have a looming spectre of a C++ analysis project, one of the goals of
the project is to be able to efficiently process huge volumes (read GBs) of
code. Given the current benchmarks of language.c compared to the g++ front
end. I was thinking of using an existing C++ parser written in C++, pro
There is language.c
http://www.sivity.net/projects/language.c/
http://hackage.haskell.org/package/language-c
>From a parsing standpoint, C++ is a massive departure from C. Good luck
though.
On Thu, Jul 16, 2009 at 12:25 PM, Roy Lowrance wrote:
> I am working on a research language that is a v
I am working on a research language that is a variant of C. I'd like
to use Parsec as the parser.
Is there an existing Parsec parser for C or C++ (or Java) that could
serve as a starting point?
Thanks, Roy
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Don Stewart wrote:
> Newbies:
> http://haskell.org
>
> Everything regular users need at fingertips
> http://dashboard.haskell.org/
That's fine. But please, no matter how minimalist
the newbie page, make sure that there is a clear
and prominent link there to the advanced page.
Otherwise, i
On Thu, Jul 16, 2009 at 12:11 PM, Heinrich
Apfelmus wrote:
>
> Generic Programming: An introduction
> http://www.cse.chalmers.se/~patrikj/poly/afp98/
>
> It's a bit verbose at times, but you only need the first few chapters to
> get an idea about polynomial functors (sums and pairs) and mu .
On Wed, Jul 15, 2009 at 11:13 PM, Don Stewart wrote:
> fernanbolando:
>> Hi all
>>
>> I recently used 2 hours of work looking for a bug that was causing
>>
>> Program error: Prelude.!!: index too large
>>
>> This is not very informative. It did not give me a hint which function
>> was causing this.
Fernan Bolando writes:
> On Thu, Jul 16, 2009 at 4:10 PM, Jon
> Fairbairn wrote:
>
>> I wonder if your code has to use !! at all? I took a look at a random
>> module from the above link, and (without making much attempt at
>> understanding it), I'd guess that using accumArray and friends would be
Call for Papers
IFL 2009
Seton Hall University
SOUTH ORANGE, NJ, USA
http://tltc.shu.edu/blogs/projects/IFL2009/
* NEW *
Registration is now opened!
Register at: http://tltc.shu.edu/blogs/projects/IFL2009/registration.html
Invited Speaker:
Benjamin C. Pierce
University of Pe
Peter Verswyvelen wrote:
> After my colleague explained me about zippers and how one could derive the
> datatype using differential rules, I had to read about it.
>
> So I started reading
> http://en.wikibooks.org/wiki/Haskell/Zippers#Mechanical_Differentiation
>
> This page contains the sentence
On Thu, Jul 16, 2009 at 4:10 PM, Jon
Fairbairn wrote:
> I wonder if your code has to use !! at all? I took a look at a random
> module from the above link, and (without making much attempt at
> understanding it), I'd guess that using accumArray and friends would be
> more appropriate. Mostly you d
> By the way, does Hat - the Haskell Tracer?
Please append: "still work".
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By the way, does Hat - the Haskell Tracer?
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2009/7/16 Marc Weber
>
>
> I recall there was another method. Yeah, I even found it (using ghci and
> set -fbreak-on-exception)
>
> http://donsbot.wordpress.com/2007/11/14/no-more-exceptions-debugging-haskell-code-with-ghci/
Careful, better use -fbreak-on-error rather than -fbreak-on-exception.
Fernan Bolando writes:
> Hi all
>
> I recently used 2 hours of work looking for a bug that was causing
>
> Program error: Prelude.!!: index too large
>
> This is not very informative. It did not give me a hint which function
> was causing this. In C adding a few printf would have helped me, but
>
On Wed, Jul 15, 2009 at 6:35 PM, Ryan Ingram wrote:
> iterate' f x = x `seq` x : iterate' f (f x)
> seems better; it doesn't evaluate list elements you don't visit.
iterate'' f x = x : (iterate'' f $! f x)
...seems the most lazy strict iterate.
(Bas wishes for a type system that can express the
On Jul 15, 2009, at 2:30 PM, Hans Aberg wrote:
If ++ could be pattern matched, what should have been the result of
"let (x++y)=[1,2,3] in (x,y)"?
It will branch. In terms of unification, you get a list of
substitutions.
f :: [a] -> ([a],[a])
f (x ++ y) = (x,y)
For an argument s, any pair
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