[Haskell-cafe] Twidge using hashtags

Hello! fairly new to twidge. Got it installed and have it setting status etc etc . I'm maintaing a local website supporting the eating of a seasonal pastry in a highly competitve fashion. A race of sorts. The contestant eating the most from january first to good friday wins. To keep the eating as

Re: [Haskell-cafe] Copy .cabal folder to diff machine/user

On 31 December 2011 11:27, Vagif Verdi wrote: > The problem is, i tried and it does not work. Cabal has absolute paths > hardcoded in many places. > So just copying folders does not work unless you copy it under the > same home folder. sed the ~/.ghc/*/package.conf.d/* files, then run ghc-pkg rec

Re: [Haskell-cafe] Plugins on ghc 7.2: GHC does not export defaultCallbacks

For anyone interested, here's a patch I came up with that seems to fix the build failure. I'm trying now to reach the relevant parties to get this included in the package. diff -rN -u old-hs-plugins/src/System/Plugins/Load.hs new-hs-plugins/src/System/Plugins/Load.hs --- old-hs-plugins/src/Sys

Re: [Haskell-cafe] Copy .cabal folder to diff machine/user

The problem is, i tried and it does not work. Cabal has absolute paths hardcoded in many places. So just copying folders does not work unless you copy it under the same home folder. On Dec 30, 4:16 pm, Ivan Lazar Miljenovic wrote: > On 31 December 2011 10:49, Vagif Verdi wrote: > > > Is it possi

Re: [Haskell-cafe] Copy .cabal folder to diff machine/user

On 31 December 2011 10:49, Vagif Verdi wrote: > Is it possible to copy .cabal and .ghc folders to different machine/ > user and develop same project over there ? If you have the same version of GHC and necessary C libraries on all machines, and they're all using the same architecture (e.g. all x8

[Haskell-cafe] Copy .cabal folder to diff machine/user

Is it possible to copy .cabal and .ghc folders to different machine/ user and develop same project over there ? Or is the only way to allow a team of developers to work on the same project is to force each one of them to install all necessary packages on their machines. __

Re: [Haskell-cafe] On the purity of Haskell

On 12/30/2011 10:10 PM, Steve Horne wrote: On 30/12/2011 10:47, Bardur Arantsson wrote: On 12/29/2011 11:06 PM, Steve Horne wrote: Calling it a straw man won't convince anyone who has the scars from being attacked by those "straw men". I've been in those arguments, being told that C has side-e

Re: [Haskell-cafe] Level of Win32 GUI support in the Haskell platform

I'm using Gtk2hs in windows (and linux) with no big problems. Cairo also works. Glade does not allow me to use accents in the user interfaces on windows, but otherwise works ok. I haven't tried wx on windows. It works on linux and it provides a more "natural" interface (gtk will look like gtk also

[Haskell-cafe] Plugins on ghc 7.2: GHC does not export defaultCallbacks

Hi all, As a getting-my-feet-wet project I was starting to look into using plugins-auto with the yesod devel server, but I was quickly stymied because the plugins package isn't building on GHC 7.2. The error I get locally is the same as the one reported by hackage[1]. In short, defaultCallbac

[Haskell-cafe] purity and the season of good will

(Whether readers would consider the post [or indeed this post] an act of trollery was mooted and mentioned several times in the original post - my thoughts at the end. I am writing this because I would have expected somebody to have said this by now. If it has been said then my sincere apologies. M

Re: [Haskell-cafe] On the purity of Haskell

On 30/12/2011 20:38, Scott Turner wrote: On 2011-12-30 14:32, Steve Horne wrote: A possible way to implement a Haskell program would be... 1. Apply rewrite rules to evaluate everything possible without executing primitive IO actions. 2. Wait until you need to run the program. 3. Cont

Re: [Haskell-cafe] On the purity of Haskell

On 30/12/2011 10:47, Bardur Arantsson wrote: On 12/29/2011 11:06 PM, Steve Horne wrote: Using similar mixed definitions to conclude that every C program is full of bugs (basically equating intentional effects with side-effects, then equating side-effects with unintentional bugs) is a fairly comm

Re: [Haskell-cafe] On the purity of Haskell

Chris Smith писал(а) в своём письме Fri, 30 Dec 2011 22:28:36 +0200: I really think that the notion of “purity” appeared to convince C programmers. It would be silly to try to explain that “Int -> IO Int” isn't really a function from Int to Int, monads, blah blah blah. So, we're saying:

Re: [Haskell-cafe] On the purity of Haskell

On 2011-12-30 14:32, Steve Horne wrote: > A possible way to implement a Haskell program would be... > > 1. Apply rewrite rules to evaluate everything possible without > executing primitive IO actions. > 2. Wait until you need to run the program. > 3. Continue applying rewrite rules to evalu

Re: [Haskell-cafe] On the purity of Haskell

On Fri, 2011-12-30 at 23:16 +0200, Artyom Kazak wrote: > Thus, your function “f” is a function indeed, which generates a list of > instructions to kernel, according to given number. Not my function, but yes, f certainly appears to be a function. Conal's concern is that if there is no possible d

Re: [Haskell-cafe] On the purity of Haskell

Chris Smith писал(а) в своём письме Fri, 30 Dec 2011 22:04:21 +0200: Computability is just a distraction here. The problem isn't whether "getAnIntFromUser" is computable... it is whether it's a function at all! Even uncomputable functions are first and foremost functions, and not being comp

Re: [Haskell-cafe] On the purity of Haskell

On Fri, 2011-12-30 at 12:24 -0600, Gregg Reynolds wrote: > No redefinition involved, just a narrowing of scope. I assume that, > since we are talking about computation, it is reasonable to limit the > discussion to the class of computable functions - which, by the way, > are about as deeply embed

Re: [Haskell-cafe] On the purity of Haskell

Donn Cave писал(а) в своём письме Fri, 30 Dec 2011 20:36:46 +0200: That's why we use terms in a sense that apply meaningfully to computer programming languages in general and Haskell in particular. To do otherwise - for example to insist on a definition of "pure" that could not even in princ

Re: [Haskell-cafe] On the purity of Haskell

On Fri, 2011-12-30 at 12:45 -0600, Gregg Reynolds wrote: > I spent some time sketching out ideas for using random variables to provide > definitions (or at least notation) for stuff like IO. I'm not sure I could > even find the notes now, but my recollection is that it seemed like a > promising ap

Re: [Haskell-cafe] On the purity of Haskell

On 30/12/2011 15:50, Gregg Reynolds wrote: On Dec 30, 2011, at 10:34 AM, Artyom Kazak wrote: Gregg Reynolds писал(а) в своём письме Fri, 30 Dec 2011 17:23:20 +0200: Regarding side-effects, they can be (informally) defined pretty simply: any non-computational effect caused by a computation

Re: [Haskell-cafe] Overloaded Quotes for Template Haskell

I'm not very familiar with monad-control, but it looks like the equivalent of liftWith from monad-control would be a function that has type "StateT S Q a -> Q (S -> (a, S))". IIUC, you are suggesting that the code would look something like "restoreT [| ... $( liftWith ( ... ) ) ... |]". Unfortuna

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 10:45 AM, Gregg Reynolds wrote: > > On Dec 30, 2011, at 11:21 AM, Conal Elliott wrote: > > > > > And I also raised a more fundamental question than whether this claim of > sameness is true, namely what is equality on IO? Without a precise & > consistent definition of equal

Re: [Haskell-cafe] On the purity of Haskell

On 30/12/2011 15:23, Gregg Reynolds wrote: Now one way of understanding all this is to say that it implicates the static/dynamic (compile-time/run-time) distinction: you don't know what e.g. IO values are until runtime, so this distinction is critical to distinguishing between pure and impure.

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 10:24 AM, Gregg Reynolds wrote: > > On Dec 30, 2011, at 11:43 AM, Conal Elliott wrote: > > roof: f is a function, and it is taking the same argument each time. >> Therefore the result is the same each time. >> >> >> That's called begging the question. f is not a function,

Re: [Haskell-cafe] (...) Random generators

On 12/30/2011 04:38 PM, Jerzy Karczmarczuk wrote: > Bardur Arantsson: >> Random streams are not referentially transparent, though, AFAICT...? >> >> Either way this thread has gone on long enough, let's not prolong it >> needlessly with this side discussion. > > Sure. > But the discussion on random

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:21 AM, Conal Elliott wrote: > > And I also raised a more fundamental question than whether this claim of > sameness is true, namely what is equality on IO? Without a precise & > consistent definition of equality, the claims like "f 42 == f (43 - 1)" are > even defined,

Re: [Haskell-cafe] On the purity of Haskell

Quoth Steve Horne , > On 30/12/2011 10:41, Bardur Arantsson wrote: >> >> This doesn't sound right to me. To me, a "side effect" is something >> which happens as a (intended or unintended) consequence of something >> else. An effect which you want to happen (e.g. by calling a procedure, >> or let

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:43 AM, Conal Elliott wrote: >> roof: f is a function, and it is taking the same argument each time. >> Therefore the result is the same each time. > > That's called begging the question. f is not a function, so I guess your > proof is flawed. > > It seems pretty clear t

Re: [Haskell-cafe] On the purity of Haskell

On 30/12/2011 10:41, Bardur Arantsson wrote: This doesn't sound right to me. To me, a "side effect" is something which happens as a (intended or unintended) consequence of something else. An effect which you want to happen (e.g. by calling a procedure, or letting the GHC runtime interpreting

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:19 AM, Heinrich Apfelmus wrote: > Conal Elliott wrote: >> Heinrich Apfelmus wrote: >>> The function >>> >>> f :: Int -> IO Int >>> f x = getAnIntFromTheUser >>= \i -> return (i+x) >>> >>> is pure according to the common definition of "pure" in the context of >>> purely fu

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:43 AM, Conal Elliott wrote: > On Fri, Dec 30, 2011 at 9:43 AM, Gregg Reynolds wrote: > >> On Dec 30, 2011, at 11:20 AM, Colin Adams wrote: >> On 30 December 2011 17:17, Gregg Reynolds wrote: >> >> On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: >>> On 30 December 2011

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:43 AM, Gregg Reynolds wrote: > On Dec 30, 2011, at 11:20 AM, Colin Adams wrote: > On 30 December 2011 17:17, Gregg Reynolds wrote: > > On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: >> On 30 December 2011 16:59, Gregg Reynolds wrote: >> >> On Fri, Dec 30, 2011 at 12:

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:11 AM, Chris Smith wrote: > >> time t: f 42 (computational process implementing func application >> begins…) >> t+1:= 1 >> t+2: 43 (… and ends) >> >> >> time t+3: f 42 >> t+4: = 2 >> t+5: 44 >> >> >> Conclusion: f 42 != f 42 > > That conclusion would on

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:20 AM, Colin Adams wrote: > > On 30 December 2011 17:17, Gregg Reynolds wrote: > > On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: > >> >> >> On 30 December 2011 16:59, Gregg Reynolds wrote: >> >>> On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus >>> wrote: >>

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:30 AM, Colin Adams wrote: > > > On 30 December 2011 17:27, Conal Elliott wrote: > >> On Fri, Dec 30, 2011 at 9:20 AM, Colin Adams >> wrote: >> >>> >>> proof: f is a function, and it is taking the same argument each time. >>> Therefore the result is the same each time.

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:19 AM, Heinrich Apfelmus < apfel...@quantentunnel.de> wrote: > Conal Elliott wrote: > > Heinrich Apfelmus wrote: >> >> The function >>> >>> f :: Int -> IO Int >>> f x = getAnIntFromTheUser >>= \i -> return (i+x) >>> >>> is pure according to the common definition of "p

Re: [Haskell-cafe] On the purity of Haskell

On 30 December 2011 17:27, Conal Elliott wrote: > On Fri, Dec 30, 2011 at 9:20 AM, Colin Adams wrote: > >> >> proof: f is a function, and it is taking the same argument each time. >> Therefore the result is the same each time. >> > > Careful of circular reasoning here. Is f actually a "function"

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:20 AM, Colin Adams wrote: > > > On 30 December 2011 17:17, Gregg Reynolds wrote: > >> >> On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: >> >> >> >> On 30 December 2011 16:59, Gregg Reynolds wrote: >> >>> >>> On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus < >>> ap

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 9:11 AM, Chris Smith wrote: > > > time t: f 42 (computational process implementing func application > > begins…) > > t+1:= 1 > > t+2: 43 (… and ends) > > > > > > time t+3: f 42 > > t+4: = 2 > > t+5: 44 > > > > > > Conclusion: f 42 != f 42 > > That conclusion

Re: [Haskell-cafe] On the purity of Haskell

On 30 December 2011 17:17, Gregg Reynolds wrote: > > On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: > > > > On 30 December 2011 16:59, Gregg Reynolds wrote: > >> >> On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus < >> apfel...@quantentunnel.de> wrote: >> >>> >>> The function >>> >>> f ::

Re: [Haskell-cafe] On the purity of Haskell

Conal Elliott wrote: Heinrich Apfelmus wrote: The function f :: Int -> IO Int f x = getAnIntFromTheUser >>= \i -> return (i+x) is pure according to the common definition of "pure" in the context of purely functional programming. That's because f 42 = f (43-1) = etc. Put differently, the

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 11:04 AM, Colin Adams wrote: > > > On 30 December 2011 16:59, Gregg Reynolds wrote: > >> On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus >> wrote: >> >> The function >> >> f :: Int -> IO Int >> f x = getAnIntFromTheUser >>= \i -> return (i+x) >> >> is pure accor

Re: [Haskell-cafe] On the purity of Haskell

> time t: f 42 (computational process implementing func application > begins…) > t+1:= 1 > t+2: 43 (… and ends) > > > time t+3: f 42 > t+4: = 2 > t+5: 44 > > > Conclusion: f 42 != f 42 That conclusion would only follow if the same IO action always produced the same result when

Re: [Haskell-cafe] On the purity of Haskell

On 30 December 2011 16:59, Gregg Reynolds wrote: > > On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus < > apfel...@quantentunnel.de> wrote: > >> >> The function >> >> f :: Int -> IO Int >> f x = getAnIntFromTheUser >>= \i -> return (i+x) >> >> is pure according to the common definition of "p

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 10:19 AM, Conal Elliott wrote: > > > On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus > wrote: > > The function > > f :: Int -> IO Int > f x = getAnIntFromTheUser >>= \i -> return (i+x) > > is pure according to the common definition of "pure" in the context of pure

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 8:12 AM, Conal Elliott wrote: > On Fri, Dec 30, 2011 at 12:52 AM, Heinrich Apfelmus < > apfel...@quantentunnel.de> wrote: > >> Conal Elliott wrote: >> >>> I wrote that post to point out the fuzziness that fuels many >>> discussion threads like this one. See also http://con

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 12:49 AM, Heinrich Apfelmus < apfel...@quantentunnel.de> wrote: > > The function > > f :: Int -> IO Int > f x = getAnIntFromTheUser >>= \i -> return (i+x) > > is pure according to the common definition of "pure" in the context of > purely functional programming. That's be

Re: [Haskell-cafe] On the purity of Haskell

On Fri, Dec 30, 2011 at 12:52 AM, Heinrich Apfelmus < apfel...@quantentunnel.de> wrote: > Conal Elliott wrote: > >> I wrote that post to point out the fuzziness that fuels many >> discussion threads like this one. See also http://conal.net/blog/posts/** >> notions-of-purity-in-haskell/

Re: [Haskell-cafe] On the purity of Haskell

On Fri, 2011-12-30 at 18:34 +0200, Artyom Kazak wrote: > I wonder: can writing to memory be called a “computational effect”? If > yes, then every computation is impure. If no, then what’s the difference > between memory and hard drive? The difference is that our operating systems draw an abstr

Re: [Haskell-cafe] On the purity of Haskell

On Dec 30, 2011, at 10:34 AM, Artyom Kazak wrote: > Gregg Reynolds писал(а) в своём письме Fri, 30 Dec 2011 > 17:23:20 +0200: > >> Regarding side-effects, they can be (informally) defined pretty simply: any >> non-computational effect caused by a computation is a side-effect. > > I wonder:

Re: [Haskell-cafe] (...) Random generators

Bardur Arantsson: Random streams are not referentially transparent, though, AFAICT...? Either way this thread has gone on long enough, let's not prolong it needlessly with this side discussion. Sure. But the discussion on randomness is /per se/ interesting, especially in a functional settin

Re: [Haskell-cafe] On the purity of Haskell

Gregg Reynolds писал(а) в своём письме Fri, 30 Dec 2011 17:23:20 +0200: Regarding side-effects, they can be (informally) defined pretty simply: any non-computational effect caused by a computation is a side-effect. I wonder: can writing to memory be called a “computational effect”? If y

Re: [Haskell-cafe] On the purity of Haskell

On Dec 29, 2011, at 2:16 PM, Steve Horne wrote: > > Of course you can extract values out of IO actions to work with them - the > bind operator does this for you nicely, providing the value as an argument to > the function you pass to the right-hand argument of the bind. But that > function ret

Re: [Haskell-cafe] Overloaded Quotes for Template Haskell

One possible option would be to make a library that has all the combinators lifted to your more general type and use "lift" or "runQ" or something similar for any quotes that need lifting, along with operations from monad-control or monad-peel to lift quotes that also need access to the StateT l

Re: [Haskell-cafe] On the purity of Haskell /Random generators

On 12/29/2011 09:39 PM, Jerzy Karczmarczuk wrote: "Truly random" numbers are very rarely used, forget about them. Well, obviously, but why should we forget about them? The usual approach(*) is to gather entropy from a truly(**) random source and use that to seed (and perhaps periodically re-

Re: [Haskell-cafe] On the purity of Haskell

On 12/29/2011 11:06 PM, Steve Horne wrote: On 29/12/2011 21:01, Chris Smith wrote: On Thu, 2011-12-29 at 18:07 +, Steve Horne wrote: By definition, an intentional effect is a side-effect. To me, it's by deceptive redefinition - and a lot of arguments rely on mixing definitions - but nonethe

Re: [Haskell-cafe] On the purity of Haskell

On 12/29/2011 07:07 PM, Steve Horne wrote: On 29/12/2011 10:05, Jerzy Karczmarczuk wrote: Sorry, a long and pseudo-philosophical treatise. Trash it before reading. Heinrich Apfelmus: You could say that side effects have been moved from functions to some other type (namely IO) in Haskell. I ha

Re: [Haskell-cafe] On the purity of Haskell

Conal Elliott wrote: I wrote that post to point out the fuzziness that fuels many discussion threads like this one. See also http://conal.net/blog/posts/notions-of-purity-in-haskell/ and the comments. I almost never find value in discussion about whether language X is "functional", "pure", or

Re: [Haskell-cafe] On the purity of Haskell

Steve Horne wrote: Heinrich Apfelmus wrote: Maybe it helps to try to find an example of a function f :: A -> B for some cleverly chosen types A,B that is not pure, i.e. does not return the same values for equal arguments. [..] For your specific challenge, place that as a left-hand argume