Re: [Haskell-cafe] Can't seem to get `par` working appropriately with lists
Felipe Lessa wrote: On Thu, Feb 21, 2008 at 8:58 AM, Luke Andrew [EMAIL PROTECTED] wrote: test2.hs: import Control.Parallel fib1 n = if n == 0 then 0 else if n == 1 then 1 else fib1 (n-1) + fib1 (n-2) fib2 n = if n == 0 then 0 else if n == 1 then 1 else fib2 (n-1) + fib2 (n-2) fiblist1 n = [fib1 x| x - [1..n]] fiblist2 n = [fib2 x| x - [1..n]] main = do print $ zipWith (+) (fiblist2 37 `par` fiblist1 37) (fiblist2 37) Besides what Jules Bean said, note also that 'par' works a bit like 'seq', only evaluating until WHNF. So even if you said main = let f1 = fiblist1 37 f2 = fiblist2 37 in print $ zipWith (+) (f2 `par` f1) f2 you still wouldn't get what you want. Why? It only evaluates f1 and f2 until it reaches [] or (_:_), and nothing more, it doesn't even try to figure out that f2 is _:_:_:_:···:[] nor it tries to see that f2 is 1:_, but you wanted that the parallel computation went until f2 was 1:1:2:3:···:[]. To do that, force the list (i.e. do a deep seq). There's Control.Parallel.Strategies to help you doing this, but if you want to reimplement it, try force [] = () force (x:xs) = x `seq` force xs main = let f1 = fiblist1 37 f2 = fiblist2 37 in print $ zipWith (+) (force f2 `par` f1) f2 'par' will try to see that 'force f2' is really (), but to do that 'force' will go all the way down thru the list forcing its spine and its values. HTH, Thanks Felipe, works as advertised. Guest I'm going to have to read up on WHNF, I just ignored it after my initial success hoped it would continue to work. Guess I should have RTFM :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Proliferation of List-Like Types
On 22 feb 2008, at 08.18, Jules Bean wrote: Thomas Schilling wrote: On 21 feb 2008, at 18.35, Johan Tibell wrote: I switched from lazy bytestrings to a left fold in my networking code after reading what Oleg wrote about streams vs folds. No problems with handles, etc. anymore. Do you fold over chunks? Can you continue to use Parsek or other utilities that need a stream-abstraction, and if so, how do you handle the end of a chunk. This is the kind of callback interface where lazy evaluation really abstracts things nicely. You can't call a stream-abstraction utility using a left-fold- enumerator without cheating (unsafeInterleave), because the stream- abstraction is incompatible (and leaky! even though it is convenient). You can convert in the other direction fine. Chunk are no problem, and convertible: you can build an element fold from a chunk fold, and a chunk fold from an element fold (as long as there is an 'end-of-input' marker). Hm, thinking about it, parsers just need to be able to return a continuation instead of fail at the end of the input. This continuation can then be invoked with the next chunk as input. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Proliferation of List-Like Types
On Fri, Feb 22, 2008 at 9:31 AM, Thomas Schilling [EMAIL PROTECTED] wrote: On 22 feb 2008, at 08.18, Jules Bean wrote: You can't call a stream-abstraction utility using a left-fold- enumerator without cheating (unsafeInterleave), because the stream- abstraction is incompatible (and leaky! even though it is convenient). You can convert in the other direction fine. Chunk are no problem, and convertible: you can build an element fold from a chunk fold, and a chunk fold from an element fold (as long as there is an 'end-of-input' marker). Hm, thinking about it, parsers just need to be able to return a continuation instead of fail at the end of the input. This continuation can then be invoked with the next chunk as input. This is what I'll do and it is also what binary-strict's [1] IncrementalGet parser does. 1. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict-0.3.0 -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Doubting Haskell
A quick note here. This is a *really* excellent tutorial on a variety
of subjects. It shows how monad operators can be used responsibly (to
clarify code, not obfuscate it), it shows how chosing a good data
structure and a good algorithm can work wonders for your code, and on
a simplistic level, it shows how to build a database in Haskell.
Would it be possible to clean this up and put it in the wiki somewhere?
Thanks
Bob
On 20 Feb 2008, at 09:58, Cale Gibbard wrote:
(I'm copying the list on this, since my reply contains a tutorial
which might be of use to other beginners.)
On 19/02/2008, Alan Carter [EMAIL PROTECTED] wrote:
Hi Cale,
On Feb 19, 2008 3:48 PM, Cale Gibbard [EMAIL PROTECTED] wrote:
Just checking up, since you haven't replied on the list. Was my
information useful? Did I miss any questions you might have had? If
you'd like, I posted some examples of using catch here:
Thanks for your enquiry! My experiment continues. I did put a
progress
report on the list - your examples together with a similar long an
short pair got me over the file opening problem, and taught me some
things about active whitespace :-) I couldn't get withFile working
(says out of scope, maybe 'cos I'm ghc 6.6 on my Mac)
Make sure to put:
import System.IO
at the top of your source file, if you haven't been. This should
import everything documented here:
http://www.haskell.org/ghc/docs/latest/html/libraries/base/System-IO.html
but it turned out the line I was looking for (collapsed from the
examples)
was:
text - readFile data.txt `catch` \_ - return
This ensures the program never loses control, crashing or becoming
unpredictable by attempting to use an invalid resource, by yielding
an
empty String if for any reason the file read fails. Then an empty
String makes it very quickly through parsing. I guess that's quite
functiony :-)
Amazing how easy once I knew how. Even stranger that I couldn't
find a
bread and butter example of it.
Then I was going very quickly for a while. My file is dumped from a
WordPress MySql table. Well formed lines have 4 tab separated fields
(I'm using pipes for tabs here):
line id | record id | property | value
Line IDs are unique and don't matter. All lines with the same record
ID give a value to a property in the same record, similar to this:
1|1|name|arthur
2|1|quest|seek holy grail
3|1|colour|blue
4|2|name|robin
5|2|quest|run away
6|2|colour|yellow
Organizing that was a joy. It took minutes:
let cutUp = tail (filter (\fields - (length fields) == 4)
(map (\x - split x '\t')
(lines text)))
This should almost certainly be a function of text:
cutUp text = tail (filter (\fields - (length fields) == 4)
(map (\x - split x '\t') (lines
text)))
I found a split on someone's blog (looking for a library tokenizer),
but I can understand it just fine. I even get to chuck out ill-formed
lines and remove the very first (which contains MySql column names)
on
the way through!
Sadly, there's no general library function for doing this. We have
words and lines (and words would work here, if your fields never have
spaces), but nobody's bothered to put anything more general for simple
splitting into the base libraries (though I'm sure there's plenty on
hackage -- MissingH has a Data.String.Utils module which contains
split and a bunch of others, for example). However, for anything more
complicated, there are also libraries like Parsec, which are generally
really effective, so I highly recommend looking at that at some point.
I then made a record to put things in, and wrote some lines to play
with it (these are the real property names):
data Entry = Entry
{ occupation:: String
, iEnjoyMyJob :: Int
, myJobIsWellDefined:: Int
, myCoworkersAreCooperative :: Int
, myWorkplaceIsStressful:: Int
, myJobIsStressful :: Int
, moraleIsGoodWhereIWork:: Int
, iGetFrustratedAtWork :: Int
}
...
let e = Entry{occupation = , iEnjoyMyJob = 0}
let f = e {occupation = alan}
let g = f {iEnjoyMyJob = 47}
putStrLn ((occupation g) ++ ++ (show (iEnjoyMyJob g)))
Then I ran into another quagmire. I think I have to use Data.Map to
build a collection of records keyed by record id, and fill them in by
working through the list of 4 item lists called cutUp. As with the
file opening problem I can find a few examples that convert a list of
tuples to a Data.Map, one to one. I found a very complex example that
convinced me a map from Int to a record is possible, but gave me no
understanding of how to do it. I spent a while trying to use foldl
before I decided it can't be appropriate (I need to pass more
values).
So I tried a couple of recursive functions, something like:
type Entries = M.Map Int Entry
...
let entries = loadEntries cutUp
...
loadEntries :: [[String]] - Entries
loadEntries [] = M.empty Entries
loadEntries [x : xs] = loadEntry
[Haskell-cafe] Tips of Conditional Expression
I know the following: [1] That the general form of conditional expression is: if * Boolean_expression* then *exp1* else *exp2 *[2] That a conditional expression must always have both a then and an elseexpression. [3] That both *exp1* and *exp2* must have the same type, which is the type of the entire conditional expression. [4] That *exp1* must be true-value and *exp2* must be false-value Reference: Discrete Mathematics Using Computer by John O'Donnell and et al. (Second Edition) My question: Is it possible that exp1 and exp 2 be different function calls of another functions (separately) elsewhere within the same program? Note: My Boolean_expression is Boolean My *exp1* is a function call elsewhere within the same program (more like a subroutine) My *exp2* is another function call also elsewhere within the same program. Tope South Africa ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tips of Conditional Expression
TOPE KAREM wrote: I know the following: [1] That the general form of conditional expression is: if *Boolean_expression* then /exp1/ else /exp2 /[2] That a conditional expression must always have both a then and an else expression. [3] That both /exp1/ and /exp2/ must have the same type, which is the type of the entire conditional expression. [4] That /exp1/ must be true-value and /exp2/ must be false-value Reference: Discrete Mathematics Using Computer by John O'Donnell and et al. (Second Edition) My question: Is it possible that exp1 and exp 2 be different function calls of another functions (separately) elsewhere within the same program? Note: My Boolean_expression is Boolean My /exp1/ is a function call elsewhere within the same program (more like a subroutine) My /exp2/ is another function call also elsewhere within the same program. I'm not sure what you're asking, but exp1 and exp2 may have (the same) function type: if cond then map else filter :: (Bool - Bool) - [Bool] - [Bool] HTH Christian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tutorial for using the state monad or a better suggestion?
So the reason I keep pinging the list so much of late is I'm currently writing a GLUT program to visualize a heirarchical clustering of 18,000+ protein-protein interaction pairs (and associated gene-ontology terms). Thanks for the help on reading CSVs, those who wrote me back... my program intitializes and displays its first image within 6 seconds, about 10 times faster and in 10 times less memory than the Java program the guy was using. Now I'm to the point of making this thing interactive, and I I'm trying to figure out the Haskell way of doing this. Last time I wrote a program like this, I made a record data type with all the state and placed it into an IORef and curried it into the GLUT callback functions. I'm going to do the same thing now if there aren't cringes and wailings from people with a better sense of pure-functional aesthetics out there on the list with a willingness to either point me towards a tutorial that would help me do this better. Keep in mind that Graphics.UI.GLUT callbacks all want to return an IO (), and thus leftover state monads at ends of functions aren't going to be acceptable to the standard library... Any ideas? Oh, currently my program state includes: The geometry I'm rendering (Ptr GLfloat vertex and color arrays), The same geometry as a display list for rendering into the selection buffer An indexed and named tree that represents the clustering A tree of text containing tooltips to display The previous current mouse position (for dragging purposes) A couple of histograms as Array.IArray.Diff.DiffArrays Various parameters for constructing rendered data out of the indexed tree (for reconstruction after a node is collapsed/expanded) So I'm carrying around some pretty bulky state; should give you some understanding as to why I thougt the record data type would be the sanest way to do this without polluting my parameter list with individual IORrefs. Oh, and again, it's not that I don't know that I can make the IORef solution work, I can and I've done it before. It's just that I thought there might be a prettier way to do this. Thanks in advance! -- Jeff ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tips of Conditional Expression
Thanks. My question is whether it can call a function (say map) previously defined elsewhere in the program. Same goes for filter. Tope On Fri, Feb 22, 2008 at 6:04 AM, Christian Maeder [EMAIL PROTECTED] wrote: TOPE KAREM wrote: I know the following: [1] That the general form of conditional expression is: if *Boolean_expression* then /exp1/ else /exp2 /[2] That a conditional expression must always have both a then and an else expression. [3] That both /exp1/ and /exp2/ must have the same type, which is the type of the entire conditional expression. [4] That /exp1/ must be true-value and /exp2/ must be false-value Reference: Discrete Mathematics Using Computer by John O'Donnell and et al. (Second Edition) My question: Is it possible that exp1 and exp 2 be different function calls of another functions (separately) elsewhere within the same program? Note: My Boolean_expression is Boolean My /exp1/ is a function call elsewhere within the same program (more like a subroutine) My /exp2/ is another function call also elsewhere within the same program. I'm not sure what you're asking, but exp1 and exp2 may have (the same) function type: if cond then map else filter :: (Bool - Bool) - [Bool] - [Bool] HTH Christian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial for using the state monad or a better suggestion?
I was trying to solve a similar problem while learning the FastCGI
package. The regular CGI package allows the use of ReaderT to hold
config data. Because FastCGI does the running of the passed in CGI
action within a few calls to alloca :: (Ptr a - IO b) - IO b, I
couldn't figure out a way to use monad transformers.
I settled on the top-level IORef trick I've seen elsewhere:
bigBallOfState_ :: IORef MyState
bigBallOfState_ = unsafePerformIO $ newIORef emptyState
{-# NOINLINE bigBallOfState_ #-}
With a few accessors:
setState :: MyState - IO ()
setState = ...
getState :: IO MyState
getState = ...
I'm not going to pretend it's good style, and it assumes you only ever
need one copy of the state everywhere in your program.
-Antoine
On Fri, Feb 22, 2008 at 8:15 AM, Jefferson Heard
[EMAIL PROTECTED] wrote:
So the reason I keep pinging the list so much of late is I'm currently
writing a GLUT program to visualize a heirarchical clustering of
18,000+ protein-protein interaction pairs (and associated
gene-ontology terms). Thanks for the help on reading CSVs, those who
wrote me back... my program intitializes and displays its first image
within 6 seconds, about 10 times faster and in 10 times less memory
than the Java program the guy was using.
Now I'm to the point of making this thing interactive, and I I'm
trying to figure out the Haskell way of doing this. Last time I wrote
a program like this, I made a record data type with all the state and
placed it into an IORef and curried it into the GLUT callback
functions. I'm going to do the same thing now if there aren't cringes
and wailings from people with a better sense of pure-functional
aesthetics out there on the list with a willingness to either point me
towards a tutorial that would help me do this better. Keep in mind
that Graphics.UI.GLUT callbacks all want to return an IO (), and thus
leftover state monads at ends of functions aren't going to be
acceptable to the standard library...
Any ideas? Oh, currently my program state includes:
The geometry I'm rendering (Ptr GLfloat vertex and color arrays),
The same geometry as a display list for rendering into the selection buffer
An indexed and named tree that represents the clustering
A tree of text containing tooltips to display
The previous current mouse position (for dragging purposes)
A couple of histograms as Array.IArray.Diff.DiffArrays
Various parameters for constructing rendered data out of the indexed
tree (for reconstruction after a node is collapsed/expanded)
So I'm carrying around some pretty bulky state; should give you some
understanding as to why I thougt the record data type would be the
sanest way to do this without polluting my parameter list with
individual IORrefs.
Oh, and again, it's not that I don't know that I can make the IORef
solution work, I can and I've done it before. It's just that I
thought there might be a prettier way to do this.
Thanks in advance!
-- Jeff
___
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___
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Re: [Haskell-cafe] Rendering TTF fonts in Haskell and OpenGL
I also have made haskell bindings to FreeType, including support for extracting glyph outlines. I haven't had time to publish it yet. Hopefully I'll get around to it soon. On Mon, Feb 18, 2008 at 5:07 AM, Jeremy Shaw [EMAIL PROTECTED] wrote: At Mon, 18 Feb 2008 01:26:17 +, Luke Palmer wrote: I have an immature, but precise and picky implementation that renders text in a ttf font to an OpenGL texture (using SDL-ttf) here: http://svn.luqui.org/svn/misc/luke/work/code/haskell/frp/Fregl/Draw.hs (It may have some dependencies in the same directory). Text support is way at the bottom. Along the same lines, I have an imcomplete, but direct binding to freetype and an incomplete binding to GLX which can be used to draw text to opengl textures: http://n-heptane.com/nhlab/repos/haskell-freetype/ http://n-heptane.com/nhlab/repos/haskell-glx/ This file contains an example of drawing text using GLX+FreeType: http://n-heptane.com/nhlab/repos/haskell-freetype/FreeTypeTest.hs This code has not been touched in a few years, so it probably needs some updates to work with ghc 6.8. Also, I believe the X11 package now has builtin support for ClientMessage, so that module can go away. j. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Tips of Conditional Expression
Am Freitag, 22. Februar 2008 15:22 schrieb TOPE KAREM: Thanks. My question is whether it can call a function (say map) previously defined elsewhere in the program. Same goes for filter. Tope Like oddlyMakeEven [] = [] oddlyMakeEven ks@(k:_) = if odd k then map (*2) ks else filter even ks ? Sure, each branch can be an arbitrarily complex expression. HTH, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rendering TTF fonts in Haskell and OpenGL
[cc-ed to hopengl list; are there many haskell opengl users not on that list, btw?] a standard package for easy-to-use, high-quality, portable font support would make a great addition to haskell's otherwise nice opengl bindings! is there a reason for going directly to freetype? from the old opengl font survey at http://www.opengl.org/resources/features/fontsurvey/ i got the impression that accessing freetype2 via ftgl might make things slightly easier, while also offering more options (geometry instead of texture fonts), or did I misread? http://ftgl.wiki.sourceforge.net/ the source doesn't seem to have changed since the end of 2004, which might imply some issues with newer compilers, etc? has anyone tried to bind to ftgl? any comments on that route? and to what extent to the haskell gui libs with opengl support allow their fonts to be used for text geometry or textures in opengl? claus - Original Message - From: Bit Connor [EMAIL PROTECTED] To: Jeremy Shaw [EMAIL PROTECTED] Cc: Haskell-cafe Cafe haskell-cafe@haskell.org Sent: Friday, February 22, 2008 2:42 PM Subject: Re: [Haskell-cafe] Rendering TTF fonts in Haskell and OpenGL I also have made haskell bindings to FreeType, including support for extracting glyph outlines. I haven't had time to publish it yet. Hopefully I'll get around to it soon. On Mon, Feb 18, 2008 at 5:07 AM, Jeremy Shaw [EMAIL PROTECTED] wrote: At Mon, 18 Feb 2008 01:26:17 +, Luke Palmer wrote: I have an immature, but precise and picky implementation that renders text in a ttf font to an OpenGL texture (using SDL-ttf) here: http://svn.luqui.org/svn/misc/luke/work/code/haskell/frp/Fregl/Draw.hs (It may have some dependencies in the same directory). Text support is way at the bottom. Along the same lines, I have an imcomplete, but direct binding to freetype and an incomplete binding to GLX which can be used to draw text to opengl textures: http://n-heptane.com/nhlab/repos/haskell-freetype/ http://n-heptane.com/nhlab/repos/haskell-glx/ This file contains an example of drawing text using GLX+FreeType: http://n-heptane.com/nhlab/repos/haskell-freetype/FreeTypeTest.hs This code has not been touched in a few years, so it probably needs some updates to work with ghc 6.8. Also, I believe the X11 package now has builtin support for ClientMessage, so that module can go away. j. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tips of Conditional Expression
TOPE KAREM wrote: Thanks. My question is whether it can call a function (say map) previously defined elsewhere in the program. Same goes for filter. I'm still not sure what to answer. If map and filter were user defined functions they may occur anywhere in your current module (or must be imported) and you can apply any argument in scope (of proper type). You could i.e. apply (if cond then map else filter) to id which is the same as if cond then map id else filter id C. On Fri, Feb 22, 2008 at 6:04 AM, Christian Maeder [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: I'm not sure what you're asking, but exp1 and exp2 may have (the same) function type: if cond then map else filter :: (Bool - Bool) - [Bool] - [Bool] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock as a markdown preprocessor
On 2/21/08 3:57 PM, Duncan Coutts wrote: Consequently there is no support in Cabal etc for those kinds of documentation. GHC, Cabal and c2hs amongst others use docbook but it's a horrible format to write and the tools to process it are very finicky (we apparently have to hard code paths to specific versions of xslt stylesheets). Hi, DocBook authoring tools have progressed tremendously in the past few years, and I disagree that the tools to process it are very finicky. If there are specific questions about making DocBook more palatable for GHC, Cabal, c2hs, others, please send them to me directly or the docbook-apps list: http://www.docbook.org/help Thanks, Keith ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Graphical graph reduction
Hi Haskell-Cafe, I'm relatively new to Haskell, but have a background with SML. One of the things that amaze me about Haskell is lazy graph reduction, e.g. how the graph unfolds during the evaluation of, say, let fibs = 1 : 1 : zipWith (+) fibs (tail fibs) in take 10 fibs Lazy lists can be simulated in SML too, but unless I do something clever with references, I end up taking exponential time to compute the n'th Fibonacci number. Now to the point: Wouldn't it be great if I had a visual tool that visually showed me the graph while the above evaluation unfolded? I could use it to show some of my co-workers to whom laziness is a mystery, what it's all about. Does anybody know if such a tool exists? I'd be grateful for pointers if it does. I very much doubt that I'm the first person who has thoughts like this, but then again, who knows. People who really know Haskell might think this is too trivial a task to really be worth spending time on. If nothing similar exists, I was thinking about creating such a tool (i.e. an interpreter with additional graph-displaying features) for a very, very small subset/dialect of Haskell. I would probably be lazy (no pun intended) and start right away with abstract syntax trees to avoid lexing and parsing and such. My language of implementation would be SML, using references as the edges of the graph. Any ideas/comments would be welcome. Kai ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tips of Conditional Expression
Thank you all. I am satisfied with all your inputs. Tope On Fri, Feb 22, 2008 at 7:17 AM, Christian Maeder [EMAIL PROTECTED] wrote: TOPE KAREM wrote: Thanks. My question is whether it can call a function (say map) previously defined elsewhere in the program. Same goes for filter. I'm still not sure what to answer. If map and filter were user defined functions they may occur anywhere in your current module (or must be imported) and you can apply any argument in scope (of proper type). You could i.e. apply (if cond then map else filter) to id which is the same as if cond then map id else filter id C. On Fri, Feb 22, 2008 at 6:04 AM, Christian Maeder [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: I'm not sure what you're asking, but exp1 and exp2 may have (the same) function type: if cond then map else filter :: (Bool - Bool) - [Bool] - [Bool] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Graphical graph reduction
2008/2/22 [EMAIL PROTECTED]: Does anybody know if such a tool exists? I'd be grateful for pointers if it does. I very much doubt that I'm the first person who has thoughts like this, but then again, who knows. People who really know Haskell might think this is too trivial a task to really be worth spending time on. If nothing similar exists, I was thinking about creating such a tool (i.e. an interpreter with additional graph-displaying features) for a very, very small subset/dialect of Haskell. I would probably be lazy (no pun intended) and start right away with abstract syntax trees to avoid lexing and parsing and such. My language of implementation would be SML, using references as the edges of the graph. Any ideas/comments would be welcome. Rather than spending time on a project specifically to do this, it seems like a great addition to GHCi's still mostly theoretical debugger. I'll understand if you don't want to take on such a project right now, though. I'm not aware of any program that does exactly what you're asking for, but I'm attaching a lambdabot interaction for your reading pleasure. I believe it will speak for itself. Baughn let fibs = 1 : 1 : zipWith (+) fibs (tail fibs) in fibs :: [Expr] lambdabot [1,1,1 + 1,1 + (1 + 1),1 + 1 + (1 + (1 + 1)),1 + (1 + 1) + (1 + 1 + (1 + (1 ... 1 -- In a demon-haunted world, science is a candle in the dark http://dresdencodak.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with Python AST
On Fri, Feb 22, 2008 at 2:42 PM, Daniel Gorín [EMAIL PROTECTED] wrote: On Feb 21, 2008, at 7:55 PM, Roel van Dijk wrote: Your solutions allows a bit more but fails with the equivalent of def foo(): for i in range(10): if i == 6: return None The loop context 'overwrites' the function context which makes the return statement illegal. I think I need a type level list. i see. how about this? if_ = If [(IntLit 6, Suite [] [Break])] (Just $ Suite [] [Return]) while_ = While (IntLit 6) (Suite [] [if_]) Nothing while2_ = While (IntLit 6) (Suite [] [Return]) Nothing foo = FunDecl $ Suite [] [while_, while2_] p = Program [foo] newtype Ident = Id String data BinOp = Add | Sub data Exp = IntLit Integer | BinOpExp BinOp Exp Exp data Ctx reqloop reqfun data True data False data Statement ctx where If :: [(Exp, Suite (Ctx reqloop reqfun))] - Maybe (Else (Ctx reqloop reqfun)) - Statement (Ctx reqloop reqfun) While :: Exp - (Suite (Ctx True reqfun)) - Maybe (Else (Ctx True reqfun)) - Statement (Ctx reqloop reqfun) Pass:: Statement (Ctx reqloop reqfun) Break :: Statement (Ctx True reqfun) Return :: Statement (Ctx reqloop True) FunDecl :: Suite (Ctx False reqfun) - Statement (Ctx False False) newtype Global = Global [Ident] data Suite ctx = Suite [Global] [Statement ctx] type Else ctx = Suite ctx newtype Program = Program [Statement (Ctx False False)] Ah, you set a specific context when needed. Very nice. Although I had to remove the Ctx type. Otherwise I need pattern matching at the type level to bind the reqLoop and reqFun type variables (is such a thing even possible?): data Statement (Ctx reqLoop reqFun) where Now I simple pass 2 type variables to my statements: data Statement reqLoop reqFun where I now have a complete Python AST and pretty printer. Onwards towards a parser! Thanks again, Roel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Graphical graph reduction
Hello dainichi, Friday, February 22, 2008, 6:55:54 PM, you wrote: If nothing similar exists, I was thinking about creating such a tool (i.e. an interpreter with additional graph-displaying features) not exactly this, but now i'm reading introduction into Q language [1] which says on p.11 The interpreter has a built-in symbolic debugger which allows you to execute a reduction sequence step by step: ..., so you may use it to demonstrate how reductions work. Q by itself is rather interesting language - haskell-like syntax, dynamic, eager with good support for laziness. btw, this manual is probably better than we have for Haskell, i've seen programmers who thinks that Haskell is hard to learn and Q is simple and may be it's just due to its manual which takes into account typical learning problems and explains obvious things (which are really obvious only for seasoned FP programmers) [1] http://switch.dl.sourceforge.net/sourceforge/q-lang/qnutshell-0.5.pdf -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Graphical graph reduction
Kai wrote: Wouldn't it be great if I had a visual tool that visually showed me the graph while the above evaluation unfolded? Does anybody know if such a tool exists? I don't know of such a tool, the closest one to that is probably the new ghci debugger. There is also a paper and accompanying website Peter Sestoft. Demonstrating Lambda Calculus Reduction. http://www.dina.kvl.dk/~sestoft/lamreduce/ but graph reduction with sharing is not covered. Slightly off topic, Twan's blog post http://twan.home.fmf.nl/blog/haskell/ simple-reflection-of-expressions.details demonstrates a neat way to figure out how (polymorphic) higher-order functions like foldr or foldl work. It would be really cool if there was a similar embedded approach for graph reduction, but I don't think that's possible. If nothing similar exists, I was thinking about creating such a tool (i.e. an interpreter with additional graph-displaying features) for a very, very small subset/dialect of Haskell. The Haskell wikibook http://en.wikibooks.org/wiki/Haskell would greatly benefit from such a tool for the chapters about graph reduction, so I'd be a potential user :) I would probably be lazy (no pun intended) and start right away with abstract syntax trees to avoid lexing and parsing and such. My language of implementation would be SML, using references as the edges of the graph. Of course, I'd prefer Haskell as the implementation language and since you want to learn Haskell anyway ... :) Concerning the graph representation, using references is probably a bad idea anyway since they're not purely functional in style. There is Martin Erwig's Functional Graph Library (Data.Graph.Inductive) shipping with ghc: Martin Erwig. Inductive Graphs and Functional Graph Algorithms. http://web.engr.oregonstate.edu/~erwig/papers/abstracts.html#JFP01 There is also Norman Ramsey, João Dias. An Applicative Control-Flow Graph Based on Huet’s Zipper. which uses a zipper to represent a control-flow graph. I'm mentioning this paper for the following quote: the mutable flow graph was big and complex, and it led to many bugs. We have replaced it by a smaller, simpler, applicative flow graph based on Huet’s (1997) zipper. The new flow graph is a success. In other words: forget mutable references :) Moreover, it's not clear whether a graph should be used at all. Well, at least concerning the _presentation_. A todo-note at the beginning of http://en.wikibooks.org/wiki/Haskell/Graph_reduction lists the possible choices, I'm currently leaning in favor of a let .. in statements in the spirit of John Maraist, Martin Odersky and Philip Wadler. The call-by-need lambda calculus. http://homepages.inf.ed.ac.uk/wadler/topics/ call-by-need.html#need-journal Overall, the main problem for a graph reduction demonstration tool to solve is not how to perform graph reduction but how to present it. The point is: the tool is unnecessary for very simple examples since those are better done by hand. But an unsophisticated tool is useless for the more complicated cases too, since no one can make sense of the output anymore! Regards, apfelmus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial for using the state monad or a better suggestion?
On Feb 22, 2008, at 9:15 , Jefferson Heard wrote: Now I'm to the point of making this thing interactive, and I I'm trying to figure out the Haskell way of doing this. Last time I wrote a program like this, I made a record data type with all the state and placed it into an IORef and curried it into the GLUT callback functions. I'm going to do the same thing now if there aren't cringes and wailings from people with a better sense of pure-functional aesthetics out there on the list with a willingness to either point me towards a tutorial that would help me do this better. Keep in mind that Graphics.UI.GLUT callbacks all want to return an IO (), and thus leftover state monads at ends of functions aren't going to be acceptable to the standard library... What I do (with gtk2hs) is visible at http://hpaste.org/3137 --- MWPState is a fairly large record. I will note that this code stores the mutable data in separate IORefs, whereas I'm told that it's better to use a single IORef with all the mutable state inside it. (For some reason I had assumed that the overhead would be higher.) That said, the wrappers make it fairly easy to refactor it. Since the IORef(s) and much of the remaining state is read-only, I use a ReaderT IO instead of StateT IO; this also turned out to be convenient for what turned out to be a significant optimization (in response to a timer firing, it collects a bunch of data and feeds it into a TreeView, and it turned out to be useful to collect it all at the front and use local to roll a modified record with the cached values). (The code in that paste is rather out of date, probably I should update it.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial for using the state monad or a better suggestion?
Thanks. There seems to be some consensus developing around using IORefs to hold all the program state. -- Jeff On Fri, Feb 22, 2008 at 12:11 PM, Brandon S. Allbery KF8NH [EMAIL PROTECTED] wrote: On Feb 22, 2008, at 9:15 , Jefferson Heard wrote: Now I'm to the point of making this thing interactive, and I I'm trying to figure out the Haskell way of doing this. Last time I wrote a program like this, I made a record data type with all the state and placed it into an IORef and curried it into the GLUT callback functions. I'm going to do the same thing now if there aren't cringes and wailings from people with a better sense of pure-functional aesthetics out there on the list with a willingness to either point me towards a tutorial that would help me do this better. Keep in mind that Graphics.UI.GLUT callbacks all want to return an IO (), and thus leftover state monads at ends of functions aren't going to be acceptable to the standard library... What I do (with gtk2hs) is visible at http://hpaste.org/3137 --- MWPState is a fairly large record. I will note that this code stores the mutable data in separate IORefs, whereas I'm told that it's better to use a single IORef with all the mutable state inside it. (For some reason I had assumed that the overhead would be higher.) That said, the wrappers make it fairly easy to refactor it. Since the IORef(s) and much of the remaining state is read-only, I use a ReaderT IO instead of StateT IO; this also turned out to be convenient for what turned out to be a significant optimization (in response to a timer firing, it collects a bunch of data and feeds it into a TreeView, and it turned out to be useful to collect it all at the front and use local to roll a modified record with the cached values). (The code in that paste is rather out of date, probably I should update it.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH -- I try to take things like a crow; war and chaos don't always ruin a picnic, they just mean you have to be careful what you swallow. -- Jessica Edwards ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell + Windows Mobile?
Bulat Ziganshin bulat.ziganshin at gmail.com writes: Hello haskell-cafe, is there any haskell implementation for Windows Mobile? does they are support creation of GUI apps and internet networking features? Hugs is available for Windows CE, (I have it on my Jornada 720), but I've only used it for non-GUI work. However with Windows Mobile 5 Microsoft decided to unilaterally remove the console drivers, instantly breaking a large number of useful Windows CE programs. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock as a markdown preprocessor
Hi Yitzchak, About -- |, -- ^, and -- $doc, we might call them markup meta-directives, since they delimit the text to be preprocessed and then produced as markup. The meta-directives and the -- line prefixes would be removed in the process. As for producing machine-readable API metadata, I hadn't been thinking along those lines, and I enthusiastically agree with you. Further factor haddock into a metadata extractor and a documentation generator. Cheers, - Conal On Fri, Feb 22, 2008 at 3:25 AM, Yitzchak Gale [EMAIL PROTECTED] wrote: Conal Elliott wrote: Pare the Haddock markup language down to very few markup directives, say just 'foo' and Foo.Bar. Other critical ones: -- | This shows which syntax this text describes. -- ^ So does this. Less critical, but usually not provided by general markup languages: -- $doc A movable documentation chunk. If Haddock itself does not parse any other markup, we must make sure to use markup that does not lock up its information. It should be something we have a parser for, or something that has good tools for turning it into some robust machine-readable format in a lossless way. The reason is that I may want to use a bit of Haskell in a much larger project that uses some other markup system for its API documentation. So, for example, if I want to integrate the output into a larger DITA project, there should be an easy way to do that. Or Doxygen, or whatever else. Then Haddock would need to have some way of outputting its own information nicely, with embedded chunks of markup. You would read that, passing each chunk of markup through its parser. Truth is, I don't see any such parser for markdown. Do you know of one? Maybe we would have to write one. I think that improving the markup capabilities of Haddock is a minor issue. The main value of Haddock is its API metadata. Haddock currently keeps most of that in its bellly, using it secretly to create its own presentation output. The biggest improvement would be getting meaningful machine-readable output. Your idea of abstracting out the markup could actually make that easier, if we keep that goal in mind as well. Thanks, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial for using the state monad or a better suggestion?
jefferson.r.heard: So the reason I keep pinging the list so much of late is I'm currently writing a GLUT program to visualize a heirarchical clustering of 18,000+ protein-protein interaction pairs (and associated gene-ontology terms). Thanks for the help on reading CSVs, those who wrote me back... my program intitializes and displays its first image within 6 seconds, about 10 times faster and in 10 times less memory than the Java program the guy was using. Wonderful. I'm glad you're making progress. Be sure to lean on the friendly Haskell consultants of -cafe@ for help as you need it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock as a markdown preprocessor
Op 22-feb-2008, om 1:54 heeft Conal Elliott het volgende geschreven: The goal redesigning for composability is that we get more for less. Haddock can focus on its speciality, namely hyperlinked Haskell code documentation, and pandoc on its, namely human- writable and -readable prose with modern features (images, friendly hyperlinks, smart quotes dashes, footnotes, super- and subscripts, pretty math, bibliography-style link specs, etc). Haddock development can focus its resources on Haskell-specific functionality, and we library writers can still use a full-featured mark-up language. While I like the idea of a very powerful authoring system, I doubt that we should mix the documentation code with the source code. It seems much clearer to me to separate such heavily-formatted documentation from the source into separate files. Of course, the source code includes comments that specify what functions do, and so provide a bit of API documentation. But such comments should contain as little formatting as possible to keep them readable in a text editor. Reinier ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rendering TTF fonts in Haskell and OpenGL
bit: I also have made haskell bindings to FreeType, including support for extracting glyph outlines. I haven't had time to publish it yet. Hopefully I'll get around to it soon. Do you need a place to host the repository? code.haskell.org is available if you want to host there. Just visit community.haskell.org and request an account. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Fwd: [Haskell-cafe] Repeated function application
This was easier for me to understand when written so, with the start value explicit times3 :: (a - a) - Int - (a - a) times3 f n !start | n == 0 = start | otherwise = times3 f (n-1) (f start) -- no stack overflow :) tTimes3 = times3 (+1) 100 0 Here, only the third arg, the start value, needs to be bangified/strictified, and it's pretty clear why. Without the bang pattern, it stack overflows. What I'm not sure of is whether this version is in fact completely equivalent to Dan's version above. I hope it is. 2008/2/21, Dan Weston [EMAIL PROTECTED]: Ben Butler-Cole wrote: Hello I was surprised to be unable to find anything like this in the standard libraries: times :: (a - a) - Int - (a - a) times f 0 = id times f n = f . (times f (n-1)) Am I missing something more general which would allow me to repeatedly apply a function to an input? Or is this not useful? Invariably, this seems to invite a stack overflow when I try this (and is usually much slower anyway). Unless f is conditionally lazy, f^n and f will have the same strictness, so there is no point in keeping nested thunks. If you apply f immediately to x, there is no stack explosion and faster runtime: times :: (a - a) - Int - (a - a) times f !n !x | n 0 = times f (n-1) (f x) | otherwise = x Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Repeated function application
On second thought... never mind. The only thing of (somewhat marginal) interest that my latest comment adds is that the second argument doesn't need to be strict. Otherwise my code is exactly identical to Dan's. 2008/2/22, Thomas Hartman [EMAIL PROTECTED]: This was easier for me to understand when written so, with the start value explicit times3 :: (a - a) - Int - (a - a) times3 f n !start | n == 0 = start | otherwise = times3 f (n-1) (f start) -- no stack overflow :) tTimes3 = times3 (+1) 100 0 Here, only the third arg, the start value, needs to be bangified/strictified, and it's pretty clear why. Without the bang pattern, it stack overflows. What I'm not sure of is whether this version is in fact completely equivalent to Dan's version above. I hope it is. 2008/2/21, Dan Weston [EMAIL PROTECTED]: Ben Butler-Cole wrote: Hello I was surprised to be unable to find anything like this in the standard libraries: times :: (a - a) - Int - (a - a) times f 0 = id times f n = f . (times f (n-1)) Am I missing something more general which would allow me to repeatedly apply a function to an input? Or is this not useful? Invariably, this seems to invite a stack overflow when I try this (and is usually much slower anyway). Unless f is conditionally lazy, f^n and f will have the same strictness, so there is no point in keeping nested thunks. If you apply f immediately to x, there is no stack explosion and faster runtime: times :: (a - a) - Int - (a - a) times f !n !x | n 0 = times f (n-1) (f x) | otherwise = x Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Repeated function application
Actually, the second argument is already strict, and the ! doesn't make it any stricter (and is therefore gratuitous): when you evaluate the conditional (n == 0), n is evaluated. Dan Thomas Hartman wrote: On second thought... never mind. The only thing of (somewhat marginal) interest that my latest comment adds is that the second argument doesn't need to be strict. Otherwise my code is exactly identical to Dan's. 2008/2/22, Thomas Hartman [EMAIL PROTECTED]: This was easier for me to understand when written so, with the start value explicit times3 :: (a - a) - Int - (a - a) times3 f n !start | n == 0 = start | otherwise = times3 f (n-1) (f start) -- no stack overflow :) tTimes3 = times3 (+1) 100 0 Here, only the third arg, the start value, needs to be bangified/strictified, and it's pretty clear why. Without the bang pattern, it stack overflows. What I'm not sure of is whether this version is in fact completely equivalent to Dan's version above. I hope it is. 2008/2/21, Dan Weston [EMAIL PROTECTED]: Ben Butler-Cole wrote: Hello I was surprised to be unable to find anything like this in the standard libraries: times :: (a - a) - Int - (a - a) times f 0 = id times f n = f . (times f (n-1)) Am I missing something more general which would allow me to repeatedly apply a function to an input? Or is this not useful? Invariably, this seems to invite a stack overflow when I try this (and is usually much slower anyway). Unless f is conditionally lazy, f^n and f will have the same strictness, so there is no point in keeping nested thunks. If you apply f immediately to x, there is no stack explosion and faster runtime: times :: (a - a) - Int - (a - a) times f !n !x | n 0 = times f (n-1) (f x) | otherwise = x Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell w/ delimited continuations
My understanding of these things is limited, but what would stop me, theoretically speaking, of making a version of ghc with these primitives added: type Prompt r reset :: (Prompt r - r) - r shift :: Prompt r - ((a - _) - r) - a (Where _ is either r or forall b. b) -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell w/ delimited continuations
You might want to take a look at http://www.haskell.org/pipermail/haskell/2007-December/020034.html which shows an implementation of delimited continuations in Haskell98 and possibly gets rid of any requirement of implementing primitives. -- ryan On 2/22/08, Taral [EMAIL PROTECTED] wrote: My understanding of these things is limited, but what would stop me, theoretically speaking, of making a version of ghc with these primitives added: type Prompt r reset :: (Prompt r - r) - r shift :: Prompt r - ((a - _) - r) - a (Where _ is either r or forall b. b) -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock as a markdown preprocessor
On Fri, Feb 22, 2008 at 10:57 AM, Reinier Lamers [EMAIL PROTECTED] wrote: [...] Of course, the source code includes comments that specify what functions do, and so provide a bit of API documentation. But such comments should contain as little formatting as possible to keep them readable in a text editor. Hi Reinier, Do you know about the [Markdown] format and the [Pandoc] processor? [Markdown] is designed for *readability* in text editors and based on common text conventions. From the [markdown] home page: The overriding design goal for Markdown's formatting syntax is to make it as readable as possible. The idea is that a Markdown-formatted document should be publishable as-is, as plain text, without looking like it's been marked up with tags or formatting instructions. While Markdown's syntax has been influenced by several existing text-to-HTML filters, the single biggest source of inspiration for Markdown's syntax is the format of plain text email. Don't take their word for it or mine. You can copy and paste this message into the [Try Pandoc] page. Regards, - Conal [Markdown]: http://daringfireball.net/projects/markdown The markdown project page [Pandoc]: http://johnmacfarlane.net/pandoc/try The Pandoc project page [Try Pandoc]: http://johnmacfarlane.net/pandoc/try Try out Pandoc for yourself ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell w/ delimited continuations
See also, http://hackage.haskell.org/cgi-bin/hackage-scripts/package/CC-delcont An implementation of multi-prompt delimited continuations based on the paper, A Monadic Framework for Delimited Continuations, by R. Kent Dybvig, Simon Peyton Jones and Amr Sabry reset :: MonadDelimitedCont p s m = (p a - m a) - m a shift :: MonadDelimitedCont p s m = p b - ((m a - m b) - m b) - m a ryani.spam: You might want to take a look at http://www.haskell.org/pipermail/haskell/2007-December/020034.html which shows an implementation of delimited continuations in Haskell98 and possibly gets rid of any requirement of implementing primitives. -- ryan On 2/22/08, Taral [EMAIL PROTECTED] wrote: My understanding of these things is limited, but what would stop me, theoretically speaking, of making a version of ghc with these primitives added: type Prompt r reset :: (Prompt r - r) - r shift :: Prompt r - ((a - _) - r) - a (Where _ is either r or forall b. b) -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Support for Transaction Memory by Sun Microsystems ..
Hello, Found this: http://www.theregister.co.uk/2007/08/21/sun_transactional_memory_rock/ http://research.sun.com/spotlight/2007/2007-08-13_transactional_memory.html vasya ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell w/ delimited continuations
On Fri, 2008-02-22 at 14:27 -0800, Taral wrote: On 2/22/08, Taral [EMAIL PROTECTED] wrote: reset :: (Prompt r - r) - r shift :: Prompt r - ((a - _) - r) - a The point of the question is about shift/reset with *these types*. I know there are implementations with other types. Nothing but sanity is stopping you. If you make a new language, you can do whatever you like. However, with shift and reset you can represent any effect, so you would utterly lose purity. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell w/ delimited continuations
On 2/22/08, Taral [EMAIL PROTECTED] wrote: reset :: (Prompt r - r) - r shift :: Prompt r - ((a - _) - r) - a The point of the question is about shift/reset with *these types*. I know there are implementations with other types. -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell w/ delimited continuations
On 2/22/08, Derek Elkins [EMAIL PROTECTED] wrote: Nothing but sanity is stopping you. If you make a new language, you can do whatever you like. However, with shift and reset you can represent any effect, so you would utterly lose purity. Can you give an example of an impure function created using these primitives? -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell w/ delimited continuations
On Fri, 2008-02-22 at 15:13 -0800, Taral wrote: On 2/22/08, Derek Elkins [EMAIL PROTECTED] wrote: Nothing but sanity is stopping you. If you make a new language, you can do whatever you like. However, with shift and reset you can represent any effect, so you would utterly lose purity. Can you give an example of an impure function created using these primitives? shift and reset but see these slides http://cs.ioc.ee/mpc-amast06/msfp/filinski-slides.pdf and/or one or both of http://citeseer.ist.psu.edu/filinski94representing.html http://citeseer.ist.psu.edu/filinski99representing.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [Haskell] Re: Re: RE: Extensible records: Static duck typing
Mark P Jones wrote:
Ben Franksen wrote:
TREX seems to be generally agreed to be too complicated to implement and
explain.
What evidence do you have for this?
Not much, I have to admit that. It basically seems to be SPJ's opinion, as
he writes in his proposal that he never got around to implementing [TREX]
in GHC. Why not? Mainly because the implementation cost turned out to be
relatively high and further claims his new proposal is considerably
simpler to implement, and [...] it is rather simpler to explain.
I also had the impression from earlier discussions that there are few people
who support the TREX idea. I could be completely wrong, though.
Speaking as somebody who
implemented Trex for Hugs (and who also witnessed Ben Gaster
build an independent implementation), I'd have to disagree
about the first part of this. As I recall, the implementation
was reasonably straightforward, and wasn't any more complicated
than other common type system extensions that I've worked on.
I'm also not sure why you think it is complicated to explain,
but I suppose that's even more subjective.
I did not say, nor did I want to imply, that this is my own opinion. I would
be extremely happy to have TREX in ghc and all the other implementations, I
just fear that it is not going to happen, at least not any time soon. In
fact I am almost completely un-biased as to which record system Haskell
gets, as long as DOES get one and preferably IN MY LIFETIME. I'd give up a
serious amount of expressive power if it brings us nearer to this goal.
Maybe this is just me being short-sighted and egotistical.
One of the most difficult things about the Trex implementation
was finding a syntax that meshed nicely with the rest of the
Haskell syntax. This is likely to be a problem for any record
system extension of Haskell---unless you're prepared to accept
a more unconventional syntax---because many of the symbols that
you might want to use ({, }, ., |, \, for example) have already
been adopted for other purposes. Ah, syntax!
Oh yes, that is indeed quite hard. One more reason for me to a prefer a
simpler system.
Cheers
Ben
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Re: [Haskell-cafe] haddock as a markdown preprocessor
On Fri, 2008-02-22 at 07:21 -0800, Keith Fahlgren wrote: On 2/21/08 3:57 PM, Duncan Coutts wrote: Consequently there is no support in Cabal etc for those kinds of documentation. GHC, Cabal and c2hs amongst others use docbook but it's a horrible format to write and the tools to process it are very finicky (we apparently have to hard code paths to specific versions of xslt stylesheets). Hi, DocBook authoring tools have progressed tremendously in the past few years, and I disagree that the tools to process it are very finicky. If there are specific questions about making DocBook more palatable for GHC, Cabal, c2hs, others, please send them to me directly or the docbook-apps list: http://www.docbook.org/help I admit to knowing rather little about it but I've noticed that these three projects are using xsltproc directly as their docbook processor (the other two just copied GHC). Because xsltproc is a general purpose tool they have to supply a large number of parameters including a hard coded location of an xslt script (and xsltproc seems to always want to go to the network to download a dtd when it already has a version it can use offline). Currently Cabal uses: xsltproc --param use.id.as.filename 1 --param toc.section.depth 3 --stringparam base.dir dist/doc/users-guide/ --stringparam html.stylesheet doc/fptools.css /usr/share/sgml/docbook/xsl-stylesheets-1.70.1/xhtml/chunk.xsl doc/Cabal.xml Yes, that's a hard coded path to the style sheet. GHC does it slightly more cleverly by using a configure.ac test to look through a very large number of hard coded paths to try and find the above style sheet. c2hs used to use docbook2html which was easier to use in terms of specifying command lines but produced worse output and didn't seem to work on more recent distros so c2hs switched to xml docbook format rather than the previous sgml format. Basically I'd like to know what tool (that is packaged on every linux distro) do I use to convert a docbook .xml file to xhtml. I took a quick look on the FAQ linked from docbook.org/help and could not immediately find what standard tools and commands I'm supposed to use. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock as a markdown preprocessor
On Sat, 2008-02-23 at 01:28 +, Duncan Coutts wrote: Basically I'd like to know what tool (that is packaged on every linux distro) do I use to convert a docbook .xml file to xhtml. I took a quick look on the FAQ linked from docbook.org/help and could not immediately find what standard tools and commands I'm supposed to use. After a bit more looking around I found the xmlto program which is packaged for my distro: xmlto xhtml doc/Cabal.xml -o doc/manual That's considerably nicer. Now all I need to do is figure out how to tell it to use a particular css file we use. I can't help noticing that the second tutorial listed on the wiki (and the first one I've found that actually tells you want tools to use) seems to suggest using xsltproc with long hard coded paths: http://opensource.bureau-cornavin.com/crash-course/en/hello-world.html Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell w/ delimited continuations
On 2/22/08, Derek Elkins [EMAIL PROTECTED] wrote: shift and reset I was under the impression that reset was a pure function. What side effects does it have? -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell w/ delimited continuations
On Fri, 2008-02-22 at 19:04 -0800, Taral wrote: On 2/22/08, Derek Elkins [EMAIL PROTECTED] wrote: shift and reset I was under the impression that reset was a pure function. What side effects does it have? It depends on how you define pure function. It's not particularly relevant and I mostly included it as I consider them a pair. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell w/ delimited continuations
On 2/22/08, Taral [EMAIL PROTECTED] wrote: shift :: Prompt r - ((a - _) - r) - a (Where _ is either r or forall b. b) It occurs to me that _ has to be r, otherwise the subcontinuation can escape. -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
