[Haskell-cafe] Showing 100% CPU usage of parallel code
Hi, I copied the program below from a reddit post of dons'. I have a dual core laptop with ubuntu hardy and ghc 6.10.1. I can see the difference when I run the program with +RTS -N2 but CPU always says 100%. I'd like an example that shows 100 -- is it not showing 100 because of my timeformat or because of the program? If it's the latter can you point me to an example that will use more cpu? Here's the output: $ cat /proc/cpuinfo | grep processor | wc -l 2 $ export TIMEFORMAT=%E real,%U user,%S sys, %P cpu $ ghc -O2 --make Par.hs -threaded $ time ./Par 1405006117752879898543142606244511569936384005711076 2.330 real,2.328 user,0.000 sys, 99.92 cpu $ time ./Par +RTS -N2 1405006117752879898543142606244511569936384005711076 1.504 real,2.316 user,0.016 sys, 100.00 cpu Here's the program: import Control.Parallel main = a `par` b `par` c `pseq` print (a + b + c) where a = ack 3 10 b = fac 42 c = fib 34 fac 0 = 1 fac n = n * fac (n-1) ack 0 n = n+1 ack m 0 = ack (m-1) 1 ack m n = ack (m-1) (ack m (n-1)) fib 0 = 0 fib 1 = 1 fib n = fib (n-1) + fib (n-2) Thanks, Jim -- View this message in context: http://www.nabble.com/Showing-%3E100--CPU-usage-of-parallel-code-tp22137081p22137081.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Showing 100% CPU usage of parallel code
Jeff Heard wrote: Jim, I'm actually not sure that time will report greater than 100% cpu on ubuntu hardy. (really not sure, and don't have it available right this moment to check). I would however try making a computation that will take a little longer and use the system monitor or /proc to look at your CPU usage rather than time. I've had good luck with GHC 6.8 using 100% cpu, so I assume 6.10 will work much better. Hi, thanks for that. The system monitor shows that I get ~160% usage, but like you I don't know if it's possible to get time to display that (on hardy, it clearly does elsewhere). The system monitor GUI is good enough, if less neat than showing it via time. Jim On Sat, Feb 21, 2009 at 10:32 AM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello Jim, Saturday, February 21, 2009, 6:17:54 PM, you wrote: main = a `par` b `par` c `pseq` print (a + b + c) two things: 1) that are grouping order? may be, a `par` (b `par` (c `pseq` print (a + b + c))) ? 2) i recommend you to use 2 *same* computations. otherwise, it's easily possible that one of them needs much more time that the rest where a = ack 3 10 b = fac 42 c = fib 34 fac 0 = 1 fac n = n * fac (n-1) ack 0 n = n+1 ack m 0 = ack (m-1) 1 ack m n = ack (m-1) (ack m (n-1)) fib 0 = 0 fib 1 = 1 fib n = fib (n-1) + fib (n-2) Thanks, Jim -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ 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 -- View this message in context: http://www.nabble.com/Showing-%3E100--CPU-usage-of-parallel-code-tp22137081p22137684.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Elevator pitch for functional programming
Hi, I will be a TA on a comparative PL course and I'm looking for small examples (ammunition) which motivate the use of Haskell and functional programming generally. The course is for 1st year Software Engineers, none of whom are likely to have used a functional language. They will all have experience programming Java and a little C++, with a few of them knowing Python, Ruby, PHP etc etc too. If anyone has code snippets which are the equivalent of an elevator pitch for FP, I would be very grateful to see them. What I want are some small concrete examples of idioms which are natural and powerful in Haskell but difficult or impossible in, say, Java. So I can produce examples of some of the things that make FP powerful, elegant, expressive etc: higher order functions, polymorphism, composition (ask them to write (.) in Java :-)), partial application and so on. I will point any interested souls to Hughes' great paper [1]. But I have little time and it might be hard to put across why they would want to do these things in the first place. I was looking for something that speaks directly to the kind of problems they face in languages like Java... Types are a good example because Java programmers generally already appreciate the help they get from compiler messages etc, so you can sell a more flexible, enhanced form of this. Purity might appeal to anyone who has longed to be able to reason about nastily complex code with a lot of shared state. Laziness, streams? Hard to do in Java (I presume) but also quite hard to sell the need. The existence of an O'Reilly book will help, especially one that can be sampled online, so I'll point them at RWH for extended concrete examples. They will need to be already sold before they will bother with that though. Thanks, Jim [1] http://www.cs.chalmers.se/~rjmh/Papers/whyfp.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Elevator pitch for functional programming
Adrian Neumann wrote: There was a thread about that: http://www.haskell.org/pipermail/haskell-cafe/2007-September/ 031402.html Thanks! I didn't literally mean elevator pitch and if I knew that thread existed would have phrased my post differently, because a list of the things that are cool about Haskell will not impress them. What I want and am finding it hard to create are examples where FP shines and, for the same problem, imperative languages look like more work. Many will think of programming solely in terms of developing websites, GUIs, database access, so I will demonstrate how strongly-typed database access can help them. Jim Am 20.01.2009 um 11:07 schrieb Jim Burton: Hi, I will be a TA on a comparative PL course and I'm looking for small examples (ammunition) which motivate the use of Haskell and functional programming generally. The course is for 1st year Software Engineers, none of whom are likely to have used a functional language. They will all have experience programming Java and a little C++, with a few of them knowing Python, Ruby, PHP etc etc too. If anyone has code snippets which are the equivalent of an elevator pitch for FP, I would be very grateful to see them. What I want are some small concrete examples of idioms which are natural and powerful in Haskell but difficult or impossible in, say, Java. So I can produce examples of some of the things that make FP powerful, elegant, expressive etc: higher order functions, polymorphism, composition (ask them to write (.) in Java :-)), partial application and so on. I will point any interested souls to Hughes' great paper [1]. But I have little time and it might be hard to put across why they would want to do these things in the first place. I was looking for something that speaks directly to the kind of problems they face in languages like Java... Types are a good example because Java programmers generally already appreciate the help they get from compiler messages etc, so you can sell a more flexible, enhanced form of this. Purity might appeal to anyone who has longed to be able to reason about nastily complex code with a lot of shared state. Laziness, streams? Hard to do in Java (I presume) but also quite hard to sell the need. The existence of an O'Reilly book will help, especially one that can be sampled online, so I'll point them at RWH for extended concrete examples. They will need to be already sold before they will bother with that though. Thanks, Jim [1] http://www.cs.chalmers.se/~rjmh/Papers/whyfp.html ___ 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 -- Jim Burton ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Elevator pitch for functional programming
Jim Burton wrote: Adrian Neumann wrote: There was a thread about that: http://www.haskell.org/pipermail/haskell-cafe/2007-September/ 031402.html Thanks! I didn't literally mean elevator pitch and if I knew that thread existed would have phrased my post differently, because a list of the things that are cool about Haskell will not impress them. What I want and am finding it hard to create are examples where FP shines and, for the same problem, imperative languages look like more work. Parallelism! Something based on dons' blog http://cgi.cse.unsw.edu.au/~dons/blog/2007/11/29#smoking-4core will be a good start. Many will think of programming solely in terms of developing websites, GUIs, database access, so I will demonstrate how strongly-typed database access can help them. Jim [...] -- View this message in context: http://www.nabble.com/Elevator-pitch-for-functional-programming-tp21560192p21565826.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Elevator pitch for functional programming
At Tue, 20 Jan 2009 12:25:00 -0800, Dan Weston wrote: Hi Dan, One of the coolest things about Haskell is the ability to refer to values not yet calculated, without having to work out the timing yourself. You want Fibonacci numbers? Well, I might but they definitely do not :-) We are talking about some maths-averse people and you would not have got to the final syllable of 'fibonacci' before all hope was lost. But I am sure there are plenty of examples that rely on laziness which will communicate. I am sure I read a blog post or something on c.l.f/c.l.h recently about lazily sorting a million numbers but can't find it. Jim Prelude let z = zipWith (+) (0:1:z) (0:z) in take 10 z [0,1,1,2,3,5,8,13,21,34] Try doing that in one line of C++. See also e.g. http://sigfpe.blogspot.com/2006/12/tying-knots-generically.html Dan Jim Burton wrote: Jim Burton wrote: Adrian Neumann wrote: There was a thread about that: http://www.haskell.org/pipermail/haskell-cafe/2007-September/ 031402.html Thanks! I didn't literally mean elevator pitch and if I knew that thread existed would have phrased my post differently, because a list of the things that are cool about Haskell will not impress them. What I want and am finding it hard to create are examples where FP shines and, for the same problem, imperative languages look like more work. Parallelism! Something based on dons' blog http://cgi.cse.unsw.edu.au/~dons/blog/2007/11/29#smoking-4core will be a good start. Many will think of programming solely in terms of developing websites, GUIs, database access, so I will demonstrate how strongly-typed database access can help them. Jim [...] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Elevator pitch for functional programming
At Tue, 20 Jan 2009 22:08:55 +0100, Henning Thielemann wrote: Jim Burton schrieb: Well, I might but they definitely do not :-) We are talking about some maths-averse people and you would not have got to the final syllable of 'fibonacci' before all hope was lost. But I am sure there are plenty of examples that rely on laziness which will communicate. I am sure I read a blog post or something on c.l.f/c.l.h recently about lazily sorting a million numbers but can't find it. Maybe they are interested in finding all equal files in a set of files. This can be done in an elegant way by sorting the files with respect to their content. Practical enough? Indeed, thanks! Jim http://hackage.haskell.org/cgi-bin/hackage-scripts/package/equal-files ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Elevator pitch for functional programming
At Tue, 20 Jan 2009 14:17:10 -0800, Ryan Ingram wrote: I recommend checking out Don Syme's slides from CUFP 2008. http://cufp.galois.com/2008/slides/ This isn't Haskell directly, it's F#, but it fits the functional programming generally, and the two languages have, relative to the universe of programming languages, more in common than they do different. There's a lot of would you rather write this? with a giant chunk of C#, followed by or this? with a few readable lines of F#. Hi, those slides look useful and inspiring. Thanks a lot. Jim -- ryan On Tue, Jan 20, 2009 at 2:07 AM, Jim Burton j...@sdf-eu.org wrote: Hi, I will be a TA on a comparative PL course and I'm looking for small examples (ammunition) which motivate the use of Haskell and functional programming generally. The course is for 1st year Software Engineers, none of whom are likely to have used a functional language. They will all have experience programming Java and a little C++, with a few of them knowing Python, Ruby, PHP etc etc too. If anyone has code snippets which are the equivalent of an elevator pitch for FP, I would be very grateful to see them. What I want are some small concrete examples of idioms which are natural and powerful in Haskell but difficult or impossible in, say, Java. So I can produce examples of some of the things that make FP powerful, elegant, expressive etc: higher order functions, polymorphism, composition (ask them to write (.) in Java :-)), partial application and so on. I will point any interested souls to Hughes' great paper [1]. But I have little time and it might be hard to put across why they would want to do these things in the first place. I was looking for something that speaks directly to the kind of problems they face in languages like Java... Types are a good example because Java programmers generally already appreciate the help they get from compiler messages etc, so you can sell a more flexible, enhanced form of this. Purity might appeal to anyone who has longed to be able to reason about nastily complex code with a lot of shared state. Laziness, streams? Hard to do in Java (I presume) but also quite hard to sell the need. The existence of an O'Reilly book will help, especially one that can be sampled online, so I'll point them at RWH for extended concrete examples. They will need to be already sold before they will bother with that though. Thanks, Jim [1] http://www.cs.chalmers.se/~rjmh/Papers/whyfp.html ___ 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] Haskell versus F#, OCaml, et. al. ...
Don Stewart-2 wrote: [...] Haskell was in the nice position of already having such a process underway, http://haskell.org/haskellwiki/Haskell_Platform Hi Don, I'm curious -- what do the images on that page represent? Can you link to readable versions? Thanks, Jim Enjoy! -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Haskell-versus-F-%2C-OCaml%2C-et.-al.-...-tp19736848p19739995.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Help using Network.Curl
At Mon, 21 Jul 2008 13:21:06 +0100, =?ISO-8859-1?Q?Chadda=EF_Fouch=E9?= wrote: 2008/7/19 Jim Burton [EMAIL PROTECTED]: opts = [CurlEncoding text/xml , CurlHttpHeaders [X-EBAY-API-COMPATIBILITY-LEVEL=++compatLevel , X-EBAY-API-DEV-NAME=++devName , X-EBAY-API-APP-NAME=++appName , X-EBAY-API-CERT-NAME=++certName , X-EBAY-API-CALL-NAME=GeteBayOfficialTime , X-EBAY-API-SITEID=0]] Isn't it : rather than = ? Just saying... (Don't know enough to be sure I'm thinking about the right thing) Is is indeed, thanks very much. I also had to change to using `perform' rather than curlPost before it would work. Cheers, Jim -- Jedaï ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Help using Network.Curl
I tried to translate that using the Network.Curl docs and ended up with the
following code, but it's not sending the post data correctly (an ebay
api error re an unsupported verb, which I am told means a malformed
request). Any ideas? The code from a perl tutorial (which works for
me, making me think that my problem is just about the right way to
post xml to a web service) follows the haskell version, which is meant
to be a straight translation of that.
Thanks,
Jim
--
[..skipped definitions of tokens etc..]
opts = [CurlEncoding text/xml
, CurlHttpHeaders [X-EBAY-API-COMPATIBILITY-LEVEL=++compatLevel
, X-EBAY-API-DEV-NAME=++devName
, X-EBAY-API-APP-NAME=++appName
, X-EBAY-API-CERT-NAME=++certName
, X-EBAY-API-CALL-NAME=GeteBayOfficialTime
, X-EBAY-API-SITEID=0]]
body = ?xml version='1.0' encoding='utf-8'?
++ GeteBayOfficialTimeRequest
xmlns=\urn:ebay:apis:eBLBaseComponents\
++ RequesterCredentials
++ eBayAuthToken++token++/eBayAuthToken
++ /RequesterCredentials
++ /GeteBayOfficialTimeRequest
url = https://api.sandbox.ebay.com/ws/api.dll;
postData = HttpPost {postName = body
, contentType = Just text/xml
, content = ContentString body
, extraHeaders = []
, showName = Nothing}
opts = []
--also tried using curlPost and setopts then perform...
main = withCurlDo (do h - initialize
curlMultiPost url opts [postData]
)
---
Original perl:
use strict;
use LWP::UserAgent;
use HTTP::Request;
use HTTP::Headers;
# define the HTTP header
my $objHeader = HTTP::Headers-new;
$objHeader-push_header('X-EBAY-API-COMPATIBILITY-LEVEL' = '391');
$objHeader-push_header('X-EBAY-API-DEV-NAME' = 'yourdevname');
$objHeader-push_header('X-EBAY-API-APP-NAME' = 'yourappname');
$objHeader-push_header('X-EBAY-API-CERT-NAME' = 'yourcertname');
$objHeader-push_header('X-EBAY-API-CALL-NAME' = 'GeteBayOfficialTime');
$objHeader-push_header('X-EBAY-API-SITEID' = '0');
$objHeader-push_header('Content-Type' = 'text/xml');
# define the XML request
my $request =
?xml version='1.0' encoding='utf-8'? .
GeteBayOfficialTimeRequest xmlns=\urn:ebay:apis:eBLBaseComponents\ .
RequesterCredentials .
eBayAuthTokenTOKENGoesHERE/eBayAuthToken .
/RequesterCredentials .
/GeteBayOfficialTimeRequest;
# make the call
my $objRequest = HTTP::Request-new(
POST,
https://api.sandbox.ebay.com/ws/api.dll;,
$objHeader,
$request
);
# deal with the response
my $objUserAgent = LWP::UserAgent-new;
my $objResponse = $objUserAgent-request($objRequest);
if (!$objResponse-is_error) {
print $objResponse-content;
}
else {
print $objResponse-error_as_HTML;
}
--
This is what I get when running my version:
$ ./curlTest
* About to connect() to api.sandbox.ebay.com port 443 (#0)
* Trying 66.135.197.133... * connected
* Connected to api.sandbox.ebay.com (66.135.197.133) port 443 (#0)
* successfully set certificate verify locations:
* CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: none
* SSL connection using AES256-SHA
* Server certificate:
*subject: /C=US/ST=California/L=San Jose/O=eBay Inc./OU=Site
Operations/CN=api.sandbox.ebay.com
*start date: 2008-01-25 00:00:00 GMT
*expire date: 2010-03-15 23:59:59 GMT
*common name: api.sandbox.ebay.com (matched)
*issuer: /C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=Terms of
use at https://www.verisign.com/rpa (c)05/CN=VeriSign Class 3 Secure Server CA
* SSL certificate verify ok.
POST /ws/api.dll HTTP/1.1
Host: api.sandbox.ebay.com
Accept: */*
Accept-Encoding: text/xml
Content-Length: 1254
Expect: 100-continue
Content-Type: multipart/form-data;
boundary=7c836e9408cd
HTTP/1.1 100 Continue
HTTP/1.1 200 OK
Date: Sat, 19 Jul 2008 20:04:12 GMT
Server: Microsoft-IIS/5.0
X-EBAY-API-POOL-NAME: ___cDRidW90YmtiZWx9b2l3aQ==
X-EBAY-API-SERVER-NAME: ___dXUucnVlYnVvNzM3KTYzKzc3LTI0KTQxPD8zPTc=
Content-Type: text/xml
Content-Length: 330
X-Cache: MISS from sjcsbagpigw02.sjc.ebay.com, MISS from
sjcsbagpigw02.sjc.ebay.com
Connection: close
* Closing connection #0
?xml version=1.0 encoding=UTF-8 ?eBayEBayTime2008-07-19
20:04:55/EBayTimeErrorsErrorCode2/CodeErrorClassRequestError/ErrorClassSeverityCode1/SeverityCodeSeveritySeriousError/SeverityLine0/LineColumn0/ColumnShortMessage![CDATA[
Unsupported verb. ]]/ShortMessage/Error/Errors/eBay
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[Haskell-cafe] Help using Network.Curl
I want to convert this code (a Hello World with the ebay API)
to the curl binding in the hope that it will handle SSL and
redirections etc better. Can someone give me some pointers please, or
a link to an example? I haven't used libcurl or Network.Curl and
can't find anything helpful...Thanks!
-
import Network.URI
import Network.HTTP
import Network.Browser
import Data.Maybe (fromJust)
mkRequest :: Request
mkRequest = Request {
rqURI = fromJust (parseURI
https://api.sandbox.ebay.com/ws/api.dll;)
, rqMethod = POST
, rqBody= body
, rqHeaders = headers
}
headers :: [Header]
headers = [Header HdrContentType text/xml
, Header (HdrCustom X-EBAY-API-COMPATIBILITY-LEVEL) 391
, Header (HdrCustom X-EBAY-API-DEV-NAME) DevName
, Header (HdrCustom X-EBAY-API-APP-NAME) AppName
, Header (HdrCustom X-EBAY-API-CERT-NAME) CertName
, Header (HdrCustom X-EBAY-API-CALL-NAME) GeteBayOfficialTime
, Header (HdrCustom X-EBAY-API-SITEID) 0
]
body = ?xml version='1.0' encoding='utf-8'?
++ GeteBayOfficialTimeRequest
xmlns=\urn:ebay:apis:eBLBaseComponents\
++ RequesterCredentials
++ eBayAuthToken++MyToken++/eBayAuthToken
++ /RequesterCredentials
++ /GeteBayOfficialTimeRequest
main = do (_, resp) - browse (request mkRequest)
print resp
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Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17986275.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! I snipped Jonathan's message just because I was commenting on the tone of your response. Sorry if you think I presented your reply out of context, but my point is that I don't think there is any need for this in any context here. I do have a right to say that, even as someone who hardly ever posts but prefers to read the list...it's owned by everybody. This isn't the same thing as censorship and you'll notice I said norms, not rules of behaviour. No one's going to stop you making yourself look silly if you insist on doing it. As for Jonathan being too big for me, erm, who is he again? :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17987734.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] problem building array package
Building array from cabal with ghc6.6: ~/array-0.1.0.0$ runhaskell Setup.hs configure Configuring array-0.1.0.0... ~/array-0.1.0.0$ runhaskell Setup.hs build Preprocessing library array-0.1.0.0... Building array-0.1.0.0... [ 1 of 10] Compiling Data.Array.Base ( Data/Array/Base.hs, dist/build/Data/Array/Base.o ) Data/Array/Base.hs:391:23: Not in scope: `Arr.numElements' Data/Array/Base.hs:1067:35: Not in scope: `ArrST.numElementsSTArray' Data/Array/Base.hs:1079:51: Not in scope: `ArrST.numElementsSTArray' Any ideas why? Thanks, Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hoogle error
Hoogling (-) (=) gives Error, your search was invalid: Parse Error: Unexpected character '=)' Is there a way to escape the input so it would work? (I wasn't really expecting the right results BTW as I think hoogle searches type signatures not patterns in definitions, right?) Thanks, Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hoogle error
On Thu, 2007-12-13 at 20:16 +, Neil Mitchell wrote: Hi Hoogling (-) (=) gives Error, your search was invalid: Parse Error: Unexpected character '=)' Is there a way to escape the input so it would work? (I wasn't really expecting the right results BTW as I think hoogle searches type signatures not patterns in definitions, right?) What were you expecting it to give you as an answer? Hi. Sorry, I should have put the question differently -- is there sometimes a need to escape hoogle input (i.e. so I could confirm there were no results, rather than getting an error)? But, thinking about it, there's no reason that this shouldn't give an error as it isn't a type sig. (I was looking for source online somewhere of the monad instance for (-) and only entered it in hoogle out of curiosity...) Sorry to waste your time! As you were :-) Jim Either you want a function named =, in which case you have to search for = - not (=) as that won't work. This is something I plan to rectify in Hoogle 4. Or you want a function which takes a function as its first argument. (a - b) - c will give you this - but not find (=) ever. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] fundeps and overlapping/undecidable instances
I have some type-level sets using fundeps working whereby equality and membership etc are predicate functions. This seems to leads to an explosion of ugly code, with `If' class constraints etc getting out of hand -- I want to treat these as relations instead so providing the definition describes everything that is 'in' and nothing that is 'out'. I've been using Oleg's paper on lightweight static resources [1] as a template for this. I want to do something like this (supposing I have an EQ relation, (:::) for consing): class Member x y instance EQ x y = Member x (y:::ys) instance Member x ys = Member x (y:::ys) But I can certainly see why this isn't possible (It's the equivalent of pattern-matching on the constraints I suppose). Do type families provide a way to do this kind of thing or do I need a different strategy altogether, involving GADTs or whatever? Thanks, [1] http://okmij.org/ftp/Computation/resource-aware-prog/tfp.pdf -- View this message in context: http://www.nabble.com/fundeps-and-overlapping-undecidable-instances-tf4962996.html#a14215583 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] fundeps and overlapping/undecidable instances
On Fri, 2007-12-07 at 12:49 -0500, Jeff Polakow wrote: Hello, You should be able to use fundeps to do exactly what you describe below. Can you make a relatively small self-contained example which exemplifies the ugliness you see? Hi Jeff, as well as a minor code explosion if Member returns a (phantom type representing a) boolean then you have to decide what to do if the element is already in -- return the set unchanged I should think, but in other cases it might not be obvious so I want this and other things to be relations. So I had class If p x y c | p x y - c where if :: p - x - y - c instance If True x y x instance If False x y y class Member el set b | el set - b where member :: el - set - b instance x Nil False instance (Eq x y c , Member x ys b , Or c d b) = Member x (y ::: ys) b (Eq and Or being more constraints that return True or False) I want a version that is only defined where the element is in the set -- not a test, an assertion. Jim -Jeff [EMAIL PROTECTED] wrote on 12/07/2007 11:24:35 AM: I have some type-level sets using fundeps working whereby equality and membership etc are predicate functions. This seems to leads to an explosion of ugly code, with `If' class constraints etc getting out of hand -- I want to treat these as relations instead so providing the definition describes everything that is 'in' and nothing that is 'out'. I've been using Oleg's paper on lightweight static resources [1] as a template for this. I want to do something like this (supposing I have an EQ relation, (:::) for consing): class Member x y instance EQ x y = Member x (y:::ys) instance Member x ys = Member x (y:::ys) But I can certainly see why this isn't possible (It's the equivalent of pattern-matching on the constraints I suppose). Do type families provide a way to do this kind of thing or do I need a different strategy altogether, involving GADTs or whatever? Thanks, [1] http://okmij.org/ftp/Computation/resource-aware-prog/tfp.pdf -- View this message in context: http://www.nabble.com/fundeps-and- overlapping-undecidable-instances-tf4962996.html#a14215583 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HTTP actions proxy server
Thank you, that's perfect. Jim stefan kersten-2 wrote: On 16.11.2007, at 13:55, Jim Burton wrote: The docs say Should be of the form http://host:port, host, host:port, or http://host; but none of the variations work. Any ideas where I might find an example of code that does this? this works for me (modulo error handling): simpleHTTP' :: Request - IO (Result Response) simpleHTTP' req = do proxy - catch (getEnv HTTP_PROXY = return . (flip Proxy Nothing)) (\_ - return NoProxy) (_, resp) - browse (setProxy proxy request req) return (Right resp) i.e. run the request in the browser monad. sk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/HTTP-actions---proxy-server-tf4815272.html#a13853610 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HTTP actions proxy server
Justin Bailey wrote: I think it needs to be a real URL: setProxy (Proxy http://myproxy:80; Nothing) Justin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe The docs say Should be of the form http://host:port, host, host:port, or http://host; but none of the variations work. Any ideas where I might find an example of code that does this? -- View this message in context: http://www.nabble.com/HTTP-actions---proxy-server-tf4815272.html#a13792542 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] HTTP actions proxy server
How would I go about converting the little get program at http://darcs.haskell.org/http/test/get.hs to use a proxy server? I tried adding a call to setProxy like this but it doesn't work: get :: URI - IO String get uri = do browse $ setProxy (Proxy myproxy:80 Nothing) eresp - simpleHTTP (request uri) resp - handleE (err . show) eresp case rspCode resp of (2,0,0) - return (rspBody resp) _ - err (httpError resp) where showRspCode (a,b,c) = map intToDigit [a,b,c] httpError resp = showRspCode (rspCode resp) ++ ++ rspReason resp Thanks. -- View this message in context: http://www.nabble.com/HTTP-actions---proxy-server-tf4815272.html#a13775608 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Upgrading X11
On Sun, 2007-11-11 at 12:44 -0500, Brent Yorgey wrote: I think you need to run autoconf autoheader (or autoreconf) first, before running Setup configure? I could be confused, but see if that helps. If that's what the problem is, the documentation definitely needs updating. -Brent Thanks Brent, autoconf autoheader fixed it. I won't volunteer to look at the docs because I have no idea why! Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Upgrading X11
I have X11 1.2.2 installed and wanted to upgrade to 1.3 (to satisfy the dependencies of another package), but Setup configure tells me I don't have the headers installed. I do, and when I configure 1.2.2 they're detected. Is this due to the newer version of Cabal? I have ghc 6.6, Cabal 1.1.6. Thanks, -- View this message in context: http://www.nabble.com/Upgrading-X11-tf4785984.html#a13691779 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiling GHC on Scientific Linux V5 [http://ftp.scientificlinux.org/linux/scientific/50/iso/i386/SL-5.0-050407-i386-DVD.iso, Build on RHEL5]
Animesh Sharma wrote: [...] Now I have to dig deeper into the release note (http://www.haskell.org/ghc/docs/6.8.1/html/users_guide/release-6-8-1.html ), one thing which has really got me interested is the introduction of debugger to GHCi. Any tutorials on how to go about it? Hi Animesh, the User's Guide is the place to go -- http://www.haskell.org/ghc/docs/latest/html/users_guide/ghci-debugger.html Regards, Ani -The Answer lies in the Genome fuzzylife.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Compiling-GHC-on-Scientific-Linux-V5--http%3A--ftp.scientificlinux.org-linux-scientific-50-iso-i386-SL-5.0-050407-i386-DVD.iso%2C-Build-on-RHEL5--tf4751963.html#a13590339 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Disjunctive Normal Form
I am trying to rewrite sentences in a logical language into DNF, and wonder if someone would point out where I'm going wrong. My dim understanding of it is that I need to move And and Not inwards and Or out, but the function below fails, for example: dnf (Or (And A B) (Or (And C D) E)) And (Or A (And (Or C E) (Or D E))) (Or B (And (Or C E) (Or D E))) data LS = Var | Not LS | And LS LS | Or LS LS --convert sentences to DNF dnf :: LS - LS dnf (And (Or s1 s2) s3) = Or (And (dnf s1) (dnf s3)) (And (dnf s2) (dnf s3)) dnf (And s1 (Or s2 s3)) = Or (And (dnf s1) (dnf s2)) (And (dnf s1) (dnf s3)) dnf (And s1 s2) = And (dnf s1) (dnf s2) dnf (Or s1 s2) = Or (dnf s1) (dnf s2) dnf (Not (Not d)) = dnf d dnf (Not (And s1 s2)) = Or (Not (dnf s1)) (Not (dnf s2)) dnf (Not (Or s1 s2))= And (Not (dnf s1)) (Not (dnf s2)) dnf s = s Thanks, Jim -- View this message in context: http://www.nabble.com/Disjunctive-Normal-Form-tf4733248.html#a13534567 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backpatching
Derek Elkins wrote: On Tue, 2007-07-31 at 23:04 -0700, Stefan O'Rear wrote: On Wed, Aug 01, 2007 at 03:44:32PM +1000, Thomas Conway wrote: This sounds like a common problem type. Is there a well known solution to this sort of problem? Mmm... logic programming? http://citeseer.ist.psu.edu/claessen00typed.html You'll only need the code for logic-variables, and even that can be simplified because your terms are non-recursive. (Even in the recursive case, a logic program like a HM typechecker usually only needs ~50 lines of prelude). If someone is interested, I did transcribe and mildly generalize the code from that paper. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Hi Derek, I'd be interested in looking at that -- have you put it online? -- View this message in context: http://www.nabble.com/Backpatching-tf4198168.html#a11945491 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hints for Euler Problem 11
Ronald Guida wrote: Hi, again. I started looking at the Euler problems [1]. I had no trouble with problems 1 through 10, but I'm stuck on problem 11. I am aware that the solutions are available ([2]), but I would rather not look just yet. [...] FWIW I used a 2D array and a function to retrieve the values in every direction from a given row,col, for each direction valid for that array index. Getting the 4 vals in each direction is done by iterating 2 functions on the (row,col) index to move in the right direction I.e., vals (row,col) = north : south : ... : [] where north = if toohigh then [] else stream (subtract 1) (id) south = if toolow then [] else stream (+1) (id) ... -- View this message in context: http://www.nabble.com/Hints-for-Euler-Problem-11-tf4114963.html#a11710468 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hints for Euler Problem 11
Jim Burton wrote: Ronald Guida wrote: Hi, again. I started looking at the Euler problems [1]. I had no trouble with problems 1 through 10, but I'm stuck on problem 11. I am aware that the solutions are available ([2]), but I would rather not look just yet. [...] FWIW I used a 2D array and a function to retrieve the values in every direction from a given row,col, for each direction valid for that array index. Getting the 4 vals in each direction is done by iterating 2 functions on the (row,col) index to move in the right direction I.e., vals (row,col) = north : south : ... : [] where north = if toohigh then [] else stream (subtract 1) (id) south = if toolow then [] else stream (+1) (id) ... where `stream' is badly named -- rather than a stream it's the 4 vals in that direction. -- View this message in context: http://www.nabble.com/Hints-for-Euler-Problem-11-tf4114963.html#a11710683 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] RE: Maintaining the community
Simon Peyton-Jones wrote: [...] We need at least one forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. (RTFM isn't polite; but The answer is supposed to be documented here (\url); let us know if that doesn't answer your qn is fine.) I'd be sorry to lose that. I fully agree and I don't mean RTFM literally. The answer is supposed to be documented here (\url)... is a very acceptable form of it...one can be brisk without being rude and I'm always grateful when someone points me in the direction of the right manual - if it's currently beyond my ken and I need to read something else first then that's my problem. I'm not going to waste your time by expecting you to read it for me and give quick answers to deep questions. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11577502 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Jules Bean wrote: Jim Burton wrote: Very timely! It's sad that haskell-cafe has so much noise now. I disagree with that characterisation. I don't mean to be pedantic, but I don't think haskell-cafe has lots of noise. I think it has lots of signal! Quite different. I think you're right actually. I was exaggerating the problem due to having woken up as a bad tempered spartan. [...] One way of protecting the community is to protect this list from drowning in noise and being a bit rough with newbies who don't do any research at all before asking is perfectly acceptable in my view. I disagree with that on two separate levels: (a) I don't think being rough with newbies is the right response. (b) I also don't think it would achieve the goal you state. Being rough with one newbie will not, in my experience, particularly prevent the next question asked by the next newbie :) All IMHO, obviously. Jules You notice I said people who do no research at all? It might be unfriendly and counter to the way things happen here, but I think the most helpful response is to tell them to do some research. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11577694 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Donald Bruce Stewart wrote: As we sit here riding the Haskell wave: [...] * Give tips on how to answer questions Answering politely, and in detail, explaining common misunderstandings is better than one word replies. * Adopt a near-zero-tolerance Be Nice policy when people answer questions We are very good here already, both on email and IRC. Very timely! It's sad that haskell-cafe has so much noise now. I haven't been around very long at all but it has gone downhill dramatically even in the last 6 months (I think I could put a date on it but lets not get into that). As well as being nice, can't you sometimes tell people to RTFM? Or, You've asked that before, or That's an FAQ, search the archive? One way of protecting the community is to protect this list from drowning in noise and being a bit rough with newbies who don't do any research at all before asking is perfectly acceptable in my view. It goes without saying that everything you say about the quality of the help here is true but I don't think you should treat us with kid gloves. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11576127 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very freaky
Andrew Coppin wrote: Jim Burton wrote: Andrew Coppin wrote: On the one hand, it feels exciting to be around a programming language where there are deep theoretical discoveries and new design territories to be explored. (Compared to Haskell, the whole C / C++ / Java / JavaScript / Delphi / VisualBasic / Perl / Python thing seems so boring.) On the other hand... WHAT THE HECK DOES ALL THAT TEXT *MEAN*?! _ I agree, it's exciting to use Haskell because of its theoretical underpinning and the sense of it as a lab for PL ideas. The other downside is that you end up with a world where most of the tools are in fact one-man research projects or small toys. There are a few good, powerful, useful things out there. (GHC and Parsec immediately spring to mind.) But there's also a vast number of really tiny projects which don't seem to be terrifically well supported. Kind of makes me sad; Haskell seems almost doomed to be a language with fantastic potential, but little real-world traction. AFAIK Haskell wasn't designed for real-world traction in the first place, but as a way of consolidating FP research efforts onto one platform, so in that sense it's a resounding success rather than doomed. It also seems to have gained some traction, and we know that FP can be an eminently practical real-world secret weapon, so the tools you're waiting for someone else to write could well be on their way. At the same time, the only evidence for this at the moment is a lot of blogs, O'Reilly investing in a book and Eternal September on haskell-cafe. If you want a language with a bigger user base or that is less confusing, there are plenty to choose from. -- View this message in context: http://www.nabble.com/Very-freaky-tf4057907.html#a11547225 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] CGI test
Andrew Coppin wrote: Greetings. Can somebody write a trivial (as in: small) program so I can test my CGI stuff without having to actually install and configure Apache? [...] You could adapt the TCP server from this tutorial - http://sequence.complete.org/node/258 Regards, -- View this message in context: http://www.nabble.com/CGI-test-tf4058260.html#a11529701 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very freaky
Andrew Coppin wrote: On the one hand, it feels exciting to be around a programming language where there are deep theoretical discoveries and new design territories to be explored. (Compared to Haskell, the whole C / C++ / Java / JavaScript / Delphi / VisualBasic / Perl / Python thing seems so boring.) On the other hand... WHAT THE HECK DOES ALL THAT TEXT *MEAN*?! _ I agree, it's exciting to use Haskell because of its theoretical underpinning and the sense of it as a lab for PL ideas. The cost of taking part in that (even as an observer) is the background knowledge and common vocabulary you need in order to make sense of a lot of the papers that you may get referred to, presuming you start asking the kind of questions that elicit answers like that. I don't think the amount of background knowledge required is actually that big but if it's missing you will feel like you're going one step forwards and two steps back. The Getting Started thread on Lambda the Ultimate is good - maybe we need a wikipage like that but of links to sources of the type theoretical background to Haskell (is there one already? I see Research Papers, which obviously has a different purpose). I don't know where the best place to start would be but, as I said in another thread Andrew, TAPL is great. Re. Curry-Howard, have a look Simon Thompson's book (online for free) http://www.cs.kent.ac.uk/people/staff/sjt/TTFP/ . Not quick reads (by any means!), but depending on your learning style, better value than asking ad hoc questions and joining the dots via blog posts/wiki pages etc. -- View this message in context: http://www.nabble.com/Very-freaky-tf4057907.html#a11530874 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem using ap -- No instance for (Monad ((-) [[a]]))
If I try a function to make a point-free version of the function in this fold -- foldr (\x ys - ys ++ map (x:) ys) [[]] :pl gives me GOA Control.Monad :pl (\x ys - ys ++ map (x:) ys) ap (++) . map . (:) GOA Control.Monad :t ap (++) . map . (:) ap (++) . map . (:) :: (Monad ((-) [[a]])) = a - [[a]] - [[a]] but this is what happens if I try to use it: GOA Control.Monad let ps = foldr (ap (++) . map . (:)) [[]] interactive:1:16: No instance for (Monad ((-) [[a]])) arising from use of `ap' at interactive:1:16-22 Possible fix: add an instance declaration for (Monad ((-) [[a]])) In the first argument of `(.)', namely `ap (++)' In the first argument of `foldr', namely `((ap (++)) . (map . (:)))' In the expression: foldr ((ap (++)) . (map . (:))) [[]] (0.00 secs, 0 bytes) What gives? -- View this message in context: http://www.nabble.com/Problem-using-apNo-instance-for-%28Monad-%28%28-%3E%29---a--%29%29-tf4036243.html#a11466625 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] N00b question
poop wrote: So I'm working my way thorough haskell, doing some programming problems, and I have this one so far: Hi, I haven't spotted the problem in your code but there's an alternative solution to Euler Problem 14 on the wiki: http://www.haskell.org/haskellwiki/Euler_problems/11_to_20#Problem_14 -- it may be helpful as a comparison? Regards, p14next n = if (mod n 2 == 0) then (div n 2) else (3*n + 1) p14seqlen n = f' 1 n where f' accum n | n == 1= accum | otherwise = f' (accum + 1) (p14next n) sndmax a b = if snd a snd b then a else b p14 n = fst (f' (0,0) n) where f' maxTuple n | n == 0= maxTuple | otherwise = f' (sndmax maxTuple (n, p14seqlen n)) (n-1) the goal is to be able to run: p14 99 and not get a stack overflow message. I read what was available on tail recursion and I think I have it working with tail recursion now, at least it gives me a stack overflow message really quickly compared to before :) I have not been able to find any documentation on seq and ($!) which was also mentioned as a way to get rid of stack overflow messages so if those are what is required an explanation of those would be most helpful. -- View this message in context: http://www.nabble.com/N00b-question-tf4010616.html#a11395620 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Tomasz Zielonka wrote: On Fri, Jun 15, 2007 at 11:31:36PM +0100, Jim Burton wrote: I think that would only work if there was one column per line...I didn't make it clear that as well as being comma separated, the delimiter is around each column, of which there are several on a line so if the delimiter is ~ a file might look like: ~sdlkfj~, ~dsdkjf~ #eo row1 ~sdf dfkj~, ~dfsd~ #eo row 2 It would be easier to experiment if you could provide us with an example input file. If you are worried about revealing sensitive information, you can change all characters other then newline, ~ and , to As, for example. An accompanying output file, for checking correctness, would be even nicer. Hi Tomasz, I can do that but they do essentially look like the example above, except with 10 - 30 columns, more data in each column, and more rows, maybe this side of a million. They are produced by an Oracle export which escapes the delimiter (often a tilde) from within the cols. The output file should have exactly one row per line, with extra newlines replaced by a string given as a param (it might be a space or a html tag -- I only just remembered this and my initial effort doesn't do it). Thanks, Jim Best regards Tomek ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Tomasz Zielonka wrote: I guess you've tried to convince Oracle to produce the right format in the first place, so there would be no need for post-processing...? We don't control that job or the first db. I wonder what would you get if you set the delimiter to be a newline ;-) eek! ;-) Best regards Tomek ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
I need to remove newlines from csv files (within columns, not at the end of entire lines). This is prior to importing into a database and was being done at my workplace by a java class for quite a while until the files processed got bigger and it proved to be too slow. (The files are up to ~250MB at the moment) It was rewritten in PL/SQL, to run after the import, which was an improvement, but it still has our creaky db server thrashing away. (You may have lots of helpful suggestions in mind, but we can't clean the data at source and AFAIK we can't do it incrementally because there is no timestamp or anything on the last change to a row from the legacy db.) We don't need a general solution - if a line ends with a delimiter we can be sure it's the end of the entire line because that's the way the csv files are generated. I had a quick go with ByteString (with no attempt at robustness etc) and although I haven't compared it properly it seems faster than what we have now. But you can easily make it faster, surely! Hints for improvement please (e.g. can I unbox anything, make anything strict, or is that handled by ByteString, is there a more efficient library function to replace the fold...?). module Main where import System.Environment (getArgs) import qualified Data.ByteString.Char8 as B --remove newlines in the middle of 'columns' clean :: Char - [B.ByteString] - [B.ByteString] clean d = foldr (\x ys - if B.null x || B.last x == d then x:ys else (B.append x $ head ys):(tail ys)) [] main = do args - getArgs if length args 2 then putStrLn Usage: crunchFile INFILE OUTFILE [DELIM] else do bs - B.readFile (args!!0) let d = if length args == 3 then head (args!!2) else '' B.writeFile (args!!1) $ (B.unlines . clean d . B.lines) bs Thanks, Jim -- View this message in context: http://www.nabble.com/Sneaking-haskell-in-the-workplacecleaning-csv-files-tf3928931.html#a11142895 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Thomas Schilling wrote: On 15 jun 2007, at 18.13, Jim Burton wrote: import qualified Data.ByteString.Char8 as B Have you tried import qualified Data.ByteString.Lazy.Char8 as B ? No -- I'll give it a try and compare them. Is laziness preferable here? Thanks, ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Sebastian Sylvan wrote: On 15/06/07, Jim Burton [EMAIL PROTECTED] wrote: [snip] Hi, Hi Sebastian, I haven't compiled this, but you get the general idea: import qualified Data.ByteString.Lazy.Char8 as B -- takes a bytestring representing the file, concats the lines -- then splits it up into real lines using the delimiter clean :: Char - B.ByteString - [B.ByteString] clean' d = B.split d . B.concat . B.lines I think that would only work if there was one column per line...I didn't make it clear that as well as being comma separated, the delimiter is around each column, of which there are several on a line so if the delimiter is ~ a file might look like: ~sdlkfj~, ~dsdkjf~ #eo row1 ~sdf dfkj~, ~dfsd~ #eo row 2 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Jason Dagit wrote: [snip] I love to see people using Haskell, especially professionally, but I have to wonder if the real tool for this job is sed? :-) Jason Maybe it is -- I've never used sed. (cue oohs and ahhs from the gallery?) But from the (unquantified) gains so far haskell may certainly be enough of an improvement to fit the bill even though I'd be interested in anything that improved on it further still. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaking haskell in the workplace -- cleaning csv files
Sebastian Sylvan wrote: A sorry, I thought the delimiter was a line delimiter. I'm trying to get to that fusion goodness by using built-in functions as much as possible... How about this one: clean del = B.map ( B.filter (/='\n') ) . B.groupBy (\x y - (x,y) /= (del,'\n')) That groupBy will group it into groups which don't have the delimiter followed by a newline in them (which is the sequence your rows end with), then it filters out newlines in each row. You might want to filter out spaces first (if there are any) so that you don't get a space between the delimiter and newline at the end... I think you still need unlines after that so is the time complexity different to the unlines . foldr (function including `last') . lines in my first post? Or is it better for another reason, such as fusion goodness? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language extensions
Andrew Coppin wrote: Haskell 98 does an excellent job of being extremely simple, yet almost unbelievably powerful. Almost every day, I am blown away by how powerful it is. I suppose it just defies belief that you could possibly need even *more* power than is already in the language... Sounds like the blub paradox ;-) and also, as I've mentioned, Haskell being simple is one of the most appealing things about it. I dislike conceptual complexity. Still, it's only my personal opinion, and the decision isn't actually up to me... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Memoization-tf3822500.html#a10832782 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language extensions
Andrew Coppin wrote: [snip] You're missing a lot of the conceptual background Possibly. I find that most of what is written about Haskell tends to be aimed at absolute beginners, or at people with multiple PhDs. (As in, people to whom arcane terms like denotational semantics actually *means* something.) I remember seeing somebody wrote a game (!!) in Haskell - despite the fact that this is obviously impossible. So I went to read the paper about how they did it... and rapidly become completely lost. I get that they used something called funtional reactive programming, but I am still mystified as to what on earth that actually is, or how it functions. But an awful lot of the more popular extensions are primarily about relaxing constraints and picking the most natural way to follow through. Hey, let's make it so that classes can have several parameters! Um... OK, that more or less makes sense. I can see uses for that. Hey, let's make it so a class instance can have one or more types associated with it! Er... well, that seems straight forward enough. Alright. Hey, let's make it so that class methods can have completely arbitrary types! Wait, what the hell? How does *that* make sense?! o_O Speaking as someone who, like you, came to the language recently and for whom many of haskell's outer corners are still confusing, I should firstly say that I can see where you're coming from but that it puzzles me as to why you think things ought to be obvious or why, when something isn't obvious to you, it must be useless? Could the answer be that it will take some time before you understand the motivation for features that don't seem natural to you? You might need some patience and study along with everything else, I know I do (and people have been generous with links to work that explains the motivation). I only say this because you seem, bizarrely, to be suggesting that you could improve things by undoing the work of all these scary people as you call them in another post, whilst admitting that you don't understand it. Hey, let's make it so you can use a type variable on the RHS that doesn't even appear on the LHS! Um... that's going to be tricky, but sure, OK. Hey, let's make it so you can implement Prolog programs inside the type system! Right, I'm getting my coat now... :-P In short, some of these relax restrictions in fairly obvious directions, and others just seem downright bizzare. It helps if you can picture a matching explicitly-typed language. I don't really understand that statement. An idea you might find helps: what you're finding with algorithms, I find with architecture when I have the extensions that let me type it. ...or that one... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Memoization-tf3822500.html#a10829748 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Arbitrary precision?
Andrew Coppin wrote: ... Likewise... Oh, by the way, thanks for the extra syntax. It's really annoying having to locate Notepad.exe on the start menu, type import Blah, save it as Thing.hs, open Windoze Explorer, locate Thing.hs, and then double-click it just so that I can try stuff out in GHCi... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe God that sounds painful. As well as reading about ghci [1] you might consider Emacs and haskell-mode for a productive environment. [1] http://www.haskell.org/ghc/docs/6.4.2/html/users_guide/ghci.html -- View this message in context: http://www.nabble.com/Arbitrary-precision--tf3700066.html#a10348633 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Playing with GHC [was Arbitrary precision?]
Andrew Coppin wrote: [...] Anyway... long ramble over... Emacs isn't my operating system of choice. I prefer to use SciTE (which is *just* a text editor - as in, it doesn't also come with an integrated toaster and alarm clock). One SciTE window open, one command prompt pointing at the source folder... seems to work fairly well. Would be nice if SciTE would colourise Haskell syntax, but since Haskell is so absurdly hard to parse, I guess that's asking a lot. ;-) Obviously you should stick with it if you're happy with it but It still sounds pretty painful to me...using haskell-mode you have highlighted code in one frame, ghci in another, resting the point over a function call displays the type, the Declarations menu allows you to jump to a function/datatype whatever, type C-L to execute the code in another frame etc -- I'd say it was worth a look unless emacs brings you out in a rash. PS. What the heck email client puts URLs in as footnotes? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Arbitrary-precision--tf3700066.html#a10349446 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Intermediate Haskell Books?
Adrian Neumann wrote: -BEGIN PGP SIGNED MESSAGE- Hash: RIPEMD160 Are there any good books about intermediate to advanced Haskell? The descriptions here http://haskell.org/haskellwiki/Books_and_tutorials aren't very helpful. Adrian I think The Fun of Programming fits that description. I don't suppose you'd call it advanced (for that first decide which parts of the leading edge you're interested in and see the resources referred to by others, esp. reading recent papers) but it is a step or two on from the introductory books and includes some really interesting code and ideas. -- View this message in context: http://www.nabble.com/Intermediate-Haskell-Books--tf3698891.html#a10349551 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec beginners problem
Chris Kuklewicz wrote: [snip] There are other modules that come with Haskell than Text.ParserCombinators.Parsec such as Text.ParserCombinators.ReadP The solution with ReadP makes for a very short 'parse' function. Note that reader is built in a recursive manner. module Morse where import Control.Monad(guard) import Text.ParserCombinators.ReadP parse = map fst . readP_to_S reader where reader = done ++ choice (map pairToReader table) done = look = guard . null return [] pairToReader (s,c) = string s fmap (c:) reader table = (.-,'A'): (-...,'B'): (-.-.,'C'): (-..,'D'): (.,'E'): (..-.,'F'): (--.,'G'): (,'H'): (..,'I'): (.---,'J'): (-.-,'K'): (.-..,'L'): (--,'M'): (-.,'N'): (---,'O'): (.--.,'P'): (--.-,'Q'): (.-.,'R'): (...,'S'): (-,'T'): (..-,'U'): (...-,'V'): (.--,'W'): (-..-,'X'): (-.--,'Y'): (--..,'Z'): [] The table is sorted which means the result of 'parse' is in sorted alphabetical order. It also does not check which are dictionary words, so it finds many solutions: *Morse length $ parse ...---..-- 5104 *Morse take 10 $ parse ...---..-- [EEAGAEEEA,EEAGAT,EEAGAEEIT,EEAGAEEU,EEAGAEIA,EEAGAEIET,EEAGAEST,EEAGAEV,EEAGAHT,EEAGAIEA] Thanks Chris, that's a neat solution and an eye opener for me -- I need to investigate the Text package I think. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Parsec beginners problem
I have a couple of questions about my first use of Parsec, which is trying
to read morse code symbols from a string. I have a map of symbols:
import qualified Data.Map as M
morsemap = M.fromList [('A', .-)
...
, ('Z', --..)]
a string to parse, like
test = ...---..--
and a Parser to read a single morse letter:
morse1 :: GenParser Char st String
morseletter = try $ M.fold ((|) . string) (string ) morsemap
which I am hoping would be equivalent to
try (string .-)
| (string -.)
...etc
| string
but I don't know what the base of the fold should be (string is wrong I
suppose) - what is the unit of |? Is there a readymade combinator for
this?
It fails anyway:
*Main run morse1 test
parse error at (line 1, column 1):
unexpected .
expecting .-
I suppose this is because the strings I'm looking for overlap but I thought
the use of try..| would avoid this error...?
Thanks,
--
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Re: [Haskell-cafe] Parsec beginners problem
Dougal Stanton wrote: This may be relevant or not, but I thought morse required a delimiting character between letters, because otherwise the message was ambiguous? I seem to recall somewhere that Parsec didn't handle non-deterministic parsings very well (or at all). D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe You could be right about delimiters, but handling the ambiguous instances is the challenge in this case, which is a Ruby Quiz [http://www.rubyquiz.com/quiz121.html] - I thought it would be a good use for Parsec, and the user guide talks about try..| as the tool for it, as in testOr2 = try (string (a)) | string (b) -- View this message in context: http://www.nabble.com/Parsec-beginners-problem-tf3657821.html#a10220154 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec beginners problem
Jim Burton wrote: Dougal Stanton wrote: This may be relevant or not, but I thought morse required a delimiting character between letters, because otherwise the message was ambiguous? I seem to recall somewhere that Parsec didn't handle non-deterministic parsings very well (or at all). D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe You could be right about delimiters, but handling the ambiguous instances is the challenge in this case, which is a Ruby Quiz [http://www.rubyquiz.com/quiz121.html] - I thought it would be a good use for Parsec, and the user guide talks about try..| as the tool for it, as in testOr2 = try (string (a)) | string (b) After posting I realised the difference between parsing (a) | (b) and parsing a | aa ... so Parsec doesn't do the latter well or at all? -- View this message in context: http://www.nabble.com/Parsec-beginners-problem-tf3657821.html#a10220156 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Perl is more learnable than Haskell
kynn wrote: Perl is a large, ugly, messy language filled with quirks and eccentricities, while Haskell is an extremely elegant language whose design is guided by a few overriding ideas. (Or so I'm told.) [snip] May I ask why you want to learn it so much, if you find it so hard? I'm sure most would disagree with me but maybe you'd be better off with perl for your one liners and scripts if it serves your purpose well. You say that you've heard Haskell is extremely elegant, but is that really the reason you want to start using it as your general purpose and scripting language? I'm also interested in it myself because of it's elegance, and in order to learn different paradigms, to explore the strength of the type system etc etc, but I'm not in a particular rush to be able to use it as the one true language for scripting or web applications, or xyz, as quite a few people lately seem to be asking about. Just curious. -- View this message in context: http://www.nabble.com/Why-Perl-is-more-learnable-than-Haskell-tf3559193.html#a9946886 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad/Functor Book
Dave-86 wrote: Given the amount of material posted at haskell.org and elsewhere explaining IO, monads and functors, has anyone considered publishing a comprehensive book explaining those subjects? (I am trying to read all the material online, but books are easier to read and don't require sitting in front of a computer to do so. Plus I can write in books :-). ) Thanks, Dave Feustel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Print out the wikibook [1]? IMO it has good coverage of Monads, more detailed than any of the textbooks I've read, and leads into CT and advanced topics that aren't really covered in any of the books (partly because a lot of it isn't Haskell 98 of course). [1] http://en.wikibooks.org/wiki/Haskell -- View this message in context: http://www.nabble.com/Monad-Functor-Book-tf3474082.html#a9752877 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Partial Evaluation
I am reading Hudak's paper Modular Domain Specific Languages and Tools [1] and am confused by his use of the term `Partial Evaluation'. I understand it to mean supplying some but not all arguments to a function, e.g. (+3) but it seems to mean something else too. This is in the context of optimising performance: We have used existing partial evaluation techniques to do this...Unfortunately, there does not currently exist a suitable, easy-to-use partial evaluator for Haskell. Our approach was to convert the Haskell program to Scheme, partially evaluate the Scheme program, and then translate back into Haskell. What does P.E, mean here? Thanks, [1] Available http://wiki.ittc.ku.edu/lambda/Image:Hudak-Modular_Domain_Specific_Languages_and_Tools.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Calendar Dates before the epoch
Bjorn Bringert-2 wrote: Use the time package (Data.Time.*). time-1.0 is in GHC 6.6 extralibs, and available from Hackage (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/time-1.0) and the development version lives at http://darcs.haskell.org/packages/time/ Thanks Björn Jim -- View this message in context: http://www.nabble.com/Calendar-Dates-before-the-epoch-tf3221685.html#a8968473 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Calendar Dates before the epoch
It seems that CalendarTime is for dates since the epoch...what do I use to handle dates before that? Sorry if this is an FAQ, I looked on the wiki and tried to find MissingH since I thought it might be in there, but don't know where to find it. I also found this from 2003 - http://www.arcknowledge.com/gmane.comp.lang.haskell.libraries/2003-11/msg00019.html - is the code in a library somewhere? Thanks. -- View this message in context: http://www.nabble.com/Calendar-Dates-before-the-epoch-tf3221685.html#a8947718 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghci stack overflow
This code produces a stack overflow in ghci when I call `makeSpiral' with large values, e.g. big enough to produce a 1001x1001 spiral. (makeSpiral produces a list of lists which form a clockwise 'spiral', it's a puzzle from mathschallenge.net.) I'm sure there is a way to increase the stack space in ghc which I will look into, but is there a way I could avoid the problem in the first place by attacking the problem differently? Does stack space run out because the list is an argument being passed around (1001x1001 versions of it)? If so would the state monad help me? data Dir = R | D | L | U deriving (Show, Eq, Enum) type Spiral = ([[Int]], Int, Dir) -- (rows, current row, next direction) rows :: Spiral - [[Int]] rows (rs, i, d) = rs currentrow :: Spiral - Int currentrow (rs, i, d) = i nextdir :: Spiral - Dir nextdir (rs, i, d) = d getrow :: Int - [[Int]] - Maybe [Int] getrow i sp = if i 0 || i = length sp then Nothing else Just (sp!!i) ndir :: Dir - Dir ndir d = if d == U then R else succ d newsp :: Spiral newsp = ([[1]], 0, R) makeSpiral :: Int - Spiral makeSpiral i = makeSpiral' 2 newsp where makeSpiral' j sp = if j i then sp else makeSpiral' (j+1) (update j sp) update :: Int - Spiral - Spiral update i (sp, cr, d) = (sp', cr', d') where oldrow = if (d == U cr' == cr cr == 0) || (d == D cr' == length sp) then [] else fromJust $ getrow cr' sp cr'| d == L || d == R = cr | d == U = if cr == 0 then 0 else cr-1 | otherwise = cr+1 cr'' = if d == U cr == 0 then -1 else cr' sp'= insertrow cr'' newrow sp newrow = case d of R - oldrow++[i] D - oldrow++[i] L - i:oldrow U - i:oldrow d' | d == R || d == L = if length oldrow == maximum (map length sp) then ndir d else d | d == U = if cr'' == -1 then ndir d else d | otherwise = if cr' == length sp then ndir d else d insertrow :: Int - [Int] - [[Int]] - [[Int]] insertrow i r rs = if i == -1 then r:rs else front++[r]++back where (front, rest) = splitAt i rs back = if null rest then [] else tail rest printSpiral :: Spiral - IO () printSpiral (sp, i, d) = putStrLn (concat $ intersperse \n (map show sp)) sumdiags :: Spiral - Int sumdiags (sp, i, d) = (sumdiags' 0 0 (+1)) + (sumdiags' 0 end (subtract 1)) - centre where row1 = sp!!0 end = length row1 - 1 halfx = (length row1 `div` 2) halfy = (length sp `div` 2) centre = (sp!!halfy)!!halfx sumdiags' row col f = if row == length sp then 0 else (sp!!row)!!col + sumdiags' (row+1) (f col) f -- View this message in context: http://www.nabble.com/ghci-stack-overflow-tf2666036.html#a7435185 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] mapAccumL - find max in-sequence subsequence
Sebastian Sylvan-2 wrote: I'm not sure I completely understand what you want, and if it needs to be cute (i.e. some clever one liner usage of a library function). But here's my get-the-job-done-solution (assuming I understood what you want): import Data.List import Data.Ord longestInSequence :: (Enum a) = [a] - Int longestInSequence = maximum . map (length . takeInSeq) . tails takeInSeq [] = [] takeInSeq [x] = [x] takeInSeq (x:y:xs) | fromEnum (succ x) == fromEnum y = x : takeInSeq (y:xs) | otherwise = takeInSeq (x:xs) /S Thanks, that's what I was looking for - and it doesn't need to be 'cute'! -- View this message in context: http://www.nabble.com/mapAccumL---find-max-in-sequence-subsequence-tf2531704.html#a7059817 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Solitaire cipher
I'm a beginner having a go at implementing the Solitaire cipher (http://www.rubyquiz.com/quiz1.html as mentioned in another post) and I'd be really grateful if you could help me improve the code to be neater use more functions from the Prelude etc, or errors (eg at the moment I can't work out why padding accumulates after encrypting, decrypting?)...Thanks. *Main decrypt $ encrypt haskell is better by miles HASKE LLISB ETTER BYMIL ESAYP X *Main decrypt $ encrypt $ decrypt $ encrypt haskell is better by miles HASKE LLISB ETTER BYMIL ESAYP X BFCRK X *Main --- import Char import Random import List import Foreign import Maybe data Card = Clubs Int | Spades Int | Diamonds Int | Hearts Int | JokerA | JokerB deriving (Show, Eq) type Deck = [Card] --cardval - clubs are face value, diamonds plus 13, and so on - Jokers are both 53 cardval :: Card - Int cardval (Clubs i)= i cardval (Diamonds i) = i+13 cardval (Hearts i) = i+26 cardval (Spades i) = i+39 cardval _= 53 isJoker:: Card - Bool isJoker JokerA = True isJoker JokerB = True isJoker _ = False --take a card to a letter card2char :: Card - Char card2char c = case c of (Clubs i)- int2alpha $ cardval c --can case fall through in haskell? (Diamonds i) - int2alpha $ cardval c (Hearts i) - int2alpha $ (cardval c-26) (Spades i) - int2alpha $ (cardval c-26) _- error (Can't make ++ show c ++ into alpha) --take a letter to int, A=1, Z=26 char2int :: Char - Int char2int = (64 `subtract`) . (ord) --take a letter to int, 1=A, Z=26 int2alpha :: Int - Char int2alpha = (chr) . (+64) splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p in_fives l = foldr (\x y - x++ ++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate (5 - length l `mod` 5) 'X') --get an ordered deck newdeck :: Deck newdeck = suit 'c' ++ suit 'd' ++ suit 'h' ++ suit 's' ++ JokerA : JokerB : [] where suit s = case s of 'c' - [Clubs i | i - [1..13]] 's' - [Spades i | i - [1..13]] 'd' - [Diamonds i | i - [1..13]] 'h' - [Hearts i | i - [1..13]] --key the deck ready to provide a keystream - move JokerA down one place, --JokerB down 2 places, perform a triplecut then a countcut keydeck :: Deck - Deck keydeck = countcut. triplecut . (movedown JokerB) . (movedown JokerB) . (movedown JokerA) --bump a card down by one place in a deck, treating the deck as circular so if the card is -- last in the deck it becomes 2nd to front not 1st movedown :: Eq a = a - [a] - [a] movedown c d = if c == last d then head d : c : init (tail d) else top ++ bot!!1 : c : (tail (tail bot)) where splt = splitAt (locate c d) d top = fst splt bot = snd splt --substitute the cards above the first joker for those below the 2nd one triplecut :: Deck - Deck triplecut d = afterLastJoker d ++ center d ++ beforeFirstJoker d where beforeFirstJoker = takeWhile (not . isJoker) afterLastJoker = reverse . beforeFirstJoker . reverse center = reverse . dropWhile (not . isJoker) . reverse . dropWhile (not . isJoker) --get the value of the last card and move that many cards from the top of deck to above the last card countcut :: Deck - Deck countcut d = init (drop n d) ++ take n d ++ [last d] where n = cardval (last d) --key the deck, read the value of the top card as n, add the nth card to stream, repeat keystream :: Deck - String keystream d = if isJoker c then keystream d' else card2char c : keystream d' where d' = keydeck d c = d'!!(cardval $ d'!!0) locate :: Eq a = a - [a] - Int locate x xs = fromJust (elemIndex x xs) clean :: String - String clean = map toUpper . filter isAlpha encrypt, decrypt :: String - String --encrypt a string using an unshuffled deck to start encrypt = process (\x y - max26 (x+y)) where max26 x = if x 26 then x-26 else x --decrypt a string using an unshuffled deck to start decrypt = process (\x y - if x = y then (x+26)-y else x-y) process :: (Int - Int - Int) - String - String process f s = in_fives $ map int2alpha $ zipWith f ints1 ints2 where str1 = clean s str2 = take (length str1) (keystream newdeck) ints1 = map char2int str1 ints2 = map char2int str2 -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6971077 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org
Re: [Haskell-cafe] Haskell beginner questions
Cybertronic wrote: Hi all, I'm pretty much new to Haskell however I'm stuck on something which is that I'm trying to create a function called display where I type in a DVD name, e.g. dvd1, it returns d (String) and the multiplication of q (Int) and i (Double) Here's what I've done so far: type Film = (Int,String,Int,Double) dvd1 :: Film dvd1 = (1, Space, 5, 9.99) display :: Product - String display (c,d,q,i) = d My display function only shows the string but unfortunately I'm stuck on how to get the display function to multiply q (Int) and i (Double) together and display it next to d. Can someone help me out please? :) I'd recommend a tutorial like http://www.cs.utah.edu/~hal/docs/daume02yaht.pdf display :: Film - String display (c,d,q,i) = d ++ ++ show (fromIntegral q * i) q needs to be converted first and show will convert the result to a string. -- View this message in context: http://www.nabble.com/Haskell-beginner-questions-tf2500050.html#a6971248 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solitaire cipher
Chris Kuklewicz wrote: There are several problems with the behavior: *Main encrypt X *Main decrypt $ encrypt TANZP X So fixing this case would be the first thing to do, followed by: *Main encrypt hello LBVJW X *Main decrypt $ encrypt hello HELLO YFRTQ X Thanks a lot, I think these are all related...some changes in_fives l = trim $ foldr (\x y - x++ ++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate n 'X') where n = if m5 == 0 then 0 else 5 - m5 m5 = length l `mod` 5 trim :: String - String trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace process :: (Int - Int - Int) - String - String process f s = if null str1 then else in_fives $ map int2alpha $ zipWith f ints1 ints2 where str1 = trim $ clean s str2 = take (length str1) (keystream newdeck) ints1 = map char2int str1 ints2 = map char2int str2 *Main decrypt $ encrypt $ decrypt $ encrypt hello HELLO *Main decrypt $ encrypt $ decrypt $ encrypt haskell is miles better HASKE LLISM ILESB ETTER *Main -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6971503 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solitaire cipher
Jón Fairbairn-2 wrote: jim burton [EMAIL PROTECTED] writes: In addition to Chris's comments, here are some more: [snip] Thanks for your comments Jon. I thought about making Cards an instance of Enum but didn't realise how helpful it would be in various places. I will use the shorter version of your function - I need to get a chance to think about how it works first to be honest. Haven't noticed divMod before - handy! -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6979284 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] split string into n parts
I want to split a string into 5 parts of equal length, with the last fifth padded if necessary, but can't get it right - here's what I've got - fifths :: String - String fifths s = fifths' 0 s where l = (length s) `div` 5 fifths' xs c [] = xs ++ (replicate (l-c) 'X') fifths' xs c (y:ys) = if c == l then fifths' (xs++[' ',y]) 0 ys else fifths' (xs++[y]) (c+1) ys which, apart from surely being uglier than need be, doesn't work: *Main fifths IDOLIKETOBEBESIDETHESEASIDE IDOLI KETOBE BESIDE THESEA SIDEXX *Main fifths 12345 1 23 45 Any thoughts? Thanks! This isn't homework BTW, I'm having a go at the ruby quiz puzzles in haskell, which seems to be a nice way to learn. -- View this message in context: http://www.nabble.com/split-string-into-n-parts-tf2496941.html#a6960346 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] split string into n parts
Paul Brown-4 wrote: Cool idea! Can you post a link for the puzzles? Thankyou! It's http://www.rubyquiz.com - They are mostly well suited to haskell, lot of mazes etc. I've done 5 or 6 with varying degrees of success but have learned a lot. This thing about strings in fifths is from #1, the solitaire cipher. As for this one, don't you want the first multiple of five larger than the length of the string? You should be able to make things simpler if you auto-pad the string from the get-go (forgive any syntax errors, as I'm just composing in a browser here...): [snip] Good plan! I will play with that. -- View this message in context: http://www.nabble.com/split-string-into-n-parts-tf2496941.html#a6961186 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] split string into n parts
Mark T.B. Carroll-2 wrote: FWIW this unholy thing works for me, fifths :: String - String fifths = splitIntoN 5 [snip] Thanks Mark. -- View this message in context: http://www.nabble.com/split-string-into-n-parts-tf2496941.html#a6961461 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] split string into n parts
Jón Fairbairn-2 wrote: At a quick glance I can't see which bit needs it. The only mention of five is where it asks to split the string into groups of five characters (not into five equal parts), padded with Xs. Oh dear, you're right. Sorry, I read in a rush. Thanks for the solution too. Jón Fairbairn-2 wrote: You can do that like this: splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p in_fives l = unfoldr (splitAtMb 5) (l ++ replicate (length l `mod` 5) 'X') To break a string into five equal parts with the last padded with Xs, try this: fifths l = let len = length l part_length = (len+4)`div`5 pad_length = 5*part_length - len in unfoldr (splitAtMb part_length) (l ++ replicate pad_length 'X') I haven't checked these at all carefully, but at least they illustrate the use of unfoldr. [aside: One might argue that the prelude ought to provide splitAtMb rather than splitAt.] -- Jón Fairbairn [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/split-string-into-n-parts-tf2496941.html#a6961825 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] split string into n parts
tweak to in_fives in_fives l = unfoldr (splitAtMb 5) (l ++ replicate (5 - length l `mod` 5) 'X') -- View this message in context: http://www.nabble.com/split-string-into-n-parts-tf2496941.html#a6961912 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
