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
On Wed, Jul 15, 2009 at 6:35 PM, Ryan Ingramryani.s...@gmail.com 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
Fernan Bolando fernanbola...@mailc.net 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
2009/7/16 Marc Weber marco-owe...@gmx.de
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
By the way, does Hat - the Haskell Tracer?
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By the way, does Hat - the Haskell Tracer?
Please append: still work.
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On Thu, Jul 16, 2009 at 4:10 PM, Jon
Fairbairnjon.fairba...@cl.cam.ac.uk 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
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:
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
Fernan Bolando fernanbola...@mailc.net writes:
On Thu, Jul 16, 2009 at 4:10 PM, Jon
Fairbairnjon.fairba...@cl.cam.ac.uk 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
On Wed, Jul 15, 2009 at 11:13 PM, Don Stewartd...@galois.com 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.
On Thu, Jul 16, 2009 at 12:11 PM, Heinrich
Apfelmusapfel...@quantentunnel.de 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
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, if I
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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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 roy.lowra...@gmail.comwrote:
I am working on a research
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++,
Thanks Rick. A perfect tip! - Roy
On Thu, Jul 16, 2009 at 12:29 PM, Rick Rrick.richard...@gmail.com 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
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
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 Lowranceroy.lowra...@gmail.com wrote:
Thanks Rick. A perfect tip! - Roy
On
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 v.dijk@gmail.com:
On Wed, Jul 15, 2009 at 3:02 AM,
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
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
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
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:
main =
On Thu, Jul 16, 2009 at 2:34 PM, Andrew
Coppinandrewcop...@btinternet.com 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
On Thu, Jul 16, 2009 at 7:45 PM, Thomas Hartmantphya...@gmail.com 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
On Thu, Jul 16, 2009 at 8:22 PM, Thomas Hartmantphya...@gmail.com 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
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
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
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.
On Thu, Jul 16, 2009 at 12:40 PM, Andrew Coppin andrewcop...@btinternet.com
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
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
On Thu, Jul 16, 2009 at 8:22 PM, Thomas Hartmantphya...@gmail.com wrote:
Is this being worked on?
On Thu, Jul 16, 2009 at 12:35 PM, Bas van Dijkv.dijk@gmail.com wrote:
I have no idea.
Yes.
Bolingbroke, Peyton-Jones. Types are calling conventions
http://lambda-the-ultimate.org/node/3319
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 is
2009/7/16 Daniel van den Eijkel d...@gmx.net:
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.
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
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:
2009/7/16 Szekeres István szeke...@iii.hu:
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
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 - f b
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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Beautiful. Can we have a version on hackage?
On Thu, Jul 16, 2009 at 5:56 PM, Job Vranishjvran...@gmail.com 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
On Thu, Jul 16, 2009 at 2:52 PM, Andrew
Coppinandrewcop...@btinternet.com 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
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
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
Coppinandrewcop...@btinternet.com wrote:
Ross Mellgren wrote:
It's not where -- let also works
Prelude let { foo x = x } in (foo 1, foo True)
(1,True)
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
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 understand
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
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]
solved. see the haskell wiki for spoiler:
http://haskell.org/haskellwiki/Blow_your_mind
2009/7/16 Thomas Hartman tphya...@gmail.com:
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
(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 Westonweston...@imageworks.com wrote:
-- different from [], sum rather than product
instance Applicative MyList where
pure x = x ::: Nil
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
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
Are you starting a new Wiki? I'd absolutely love to have that resource.
On Thu, Jul 16, 2009 at 8:14 PM, Thomas
DuBuissonthomas.dubuis...@gmail.com 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
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 Enkvane...@gmail.com 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
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
DuBuissonthomas.dubuis...@gmail.com 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
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
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 not
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
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