[GHC] #6135: Unboxed Booleans
#6135: Unboxed Booleans
--+-
Reporter: benl | Owner:
Type: feature request | Status: new
Priority: normal| Component: Compiler
Version: 7.4.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby:| Blocking:
Related:|
--+-
Right now the only way to compare two integers is with primops that
produce boxed bools:
{{{
# :: Int# - Int# - Bool
==# :: Int# - Int# - Bool
}}}
To consume the resulting {{{Bool}}} we need a case-expression, which
introduces branches into the core IR and object code. Case expressions are
bad in the presence of heavy inlining because case-of-case performed by
the GHC simplifier tends to duplicate code (like in DPH and Repa
programs). Mis-predicted branches are bad in object code because they
stall the pipeline.
Consider the following expression:
{{{
case x # 0# || x =# aWidth
|| y # 0# || y =# aHeight of
True - ...
False - ...
}}}
This is very common in array programming. Ideally, it should turn into
some straight-line code to compute the flag, and then a single branch
instruction once we've worked out what alternative to take. However, as
the only way to consume the {{{Bool}}}s produced by the comparisons is to
introduce more case expressions, we end up with *four* cases in the core
IR.
What I want is this:
{{{
data Bool#
(.#) :: Int# - Int# - Bool#
(.==#) :: Int# - Int# - Bool#
(.||#) :: Bool# - Bool# - Bool#
casex .# 0# .||# x .=# aWidth
.||# y .# 0# .||# y .=# aHeight of
True# - ...
False# - ...
}}}
Bool# is the type of one bit integers. I can compute with them
algebraically and be sure that I'll get at most one branch instruction in
the resulting object code.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/6135
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[GHC] #6136: gettimeofday should not be used to schedule timeouts
#6136: gettimeofday should not be used to schedule timeouts --+- Reporter: DanielWaterworth | Owner: Type: bug | Status: new Priority: normal| Component: libraries/base Version: 7.4.1 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Testcase: Blockedby:| Blocking: Related:| --+- From what I can tell, [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/GHC- Event-Clock.html#getCurrentTime getCurrentTime] uses gettimeofday and is used in [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/GHC- Event-Manager.html#registerTimeout registerTimeout] for the purpose of scheduling timeouts. I recommend reading [http://blog.habets.pp.se/2010/09 /gettimeofday-should-never-be-used-to-measure-time this] for an explanation of why this isn't a good idea. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/6136 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #6136: gettimeofday should not be used to schedule timeouts
#6136: gettimeofday should not be used to schedule timeouts ---+ Reporter: DanielWaterworth | Owner: Type: bug | Status: closed Priority: normal| Milestone: 7.6.1 Component: libraries/base|Version: 7.4.1 Resolution: duplicate | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase:| Blockedby: Blocking:|Related: #5865 ---+ Changes (by pcapriotti): * status: new = closed * difficulty: = Unknown * resolution: = duplicate * related: = #5865 * milestone: = 7.6.1 Comment: Thanks for the report. We already switched to monotonic timers in HEAD. See #5865. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/6136#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #6136: gettimeofday should not be used to schedule timeouts
#6136: gettimeofday should not be used to schedule timeouts ---+ Reporter: DanielWaterworth | Owner: Type: bug | Status: closed Priority: normal| Milestone: 7.6.1 Component: libraries/base|Version: 7.4.1 Resolution: duplicate | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase:| Blockedby: Blocking:|Related: #5865 ---+ Comment(by DanielWaterworth): Thanks! -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/6136#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5936: Support for data families in generics
#5936: Support for data families in generics -+-- Reporter: reinerp | Owner: dreixel Type: feature request | Status: patch Priority: normal| Milestone: Component: Compiler | Version: 7.4.1 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Changes (by bgamari): * cc: bgamari@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5936#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5936: Support for data families in generics
#5936: Support for data families in generics -+-- Reporter: reinerp | Owner: dreixel Type: feature request | Status: patch Priority: normal| Milestone: Component: Compiler | Version: 7.4.1 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Comment(by bgamari): Any thoughts on how to move forward on this? -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5936#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5936: Support for data families in generics
#5936: Support for data families in generics -+-- Reporter: reinerp | Owner: dreixel Type: feature request | Status: patch Priority: normal| Milestone: Component: Compiler | Version: 7.4.1 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Comment(by dreixel): Replying to [comment:6 bgamari]: Any thoughts on how to move forward on this? I don't think it'll be too hard; I've just been very busy with deadlines. Hope to have a look at it next week. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5936#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [Haskell] (no subject)
wow look into this http://www.stenews.net/biz/?read=3610300 ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell-cafe] Fundeps and overlapping instances
2012/5/31 Iavor Diatchki iavor.diatc...@gmail.com: Hello, the notion of a functional dependency is well established, and it was used well before it was introduced to Haskell (for example, take a look at http://en.wikipedia.org/wiki/Functional_dependency). So I'd be weary to redefine it lightly. Indeed, GHC's functional dependencies are not the same. I see you have already talked about this on the GHC bug tracker. http://hackage.haskell.org/trac/ghc/ticket/1241 1. Check that an instance is consistent with itself. For example, this should be rejected: instance C a b because it allows C Int Bool and C Int Char which violate the functional dependency. This check may not always be as straightforward. When would this be a valid instance? instance K a b ⇒ C a b With a few extra extensions, K could be a type family. C currently has the kind (a - b - Constraint), with no mention of functional dependencies. Perhaps the kind of C should include the functional dependencies of C? Etienne Laurin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Troubles understanding Parsec Error Handling
Hello Thanks for the quick help with this. I thought about the idea that lookAhead might be the cause of the positioning bug but then discarded that idea because I thought lookAhead should never lead to an error past wherever the input position is now considering it doesn't consume any input. I am aware of the issue with the error message position and the output, I was still working on improving that when I was puzzled by the fact that the error message I specified wasn't even returned to me. As for try, I believe I need it to make sure the input I consume one character at the time, before I know if I will reach another valid match (or any at all) does not stay consumed when my parser fails. I am still very much in the experimental phase as far as writing Parsec combinators beyond very simple stuff is concerned so I am open for suggestions on how to improve it in a way that doesn't need try. Thanks again for all the help and especially for the patch. After applying it I do get the error message I specified. I noticed there are still some other problems in the code. In particular it doesn't work as intended in cases like this one: parseTest (do; r1 - anyOf [Hello, Hallo, Foo, HallofFame]; r2 - string fbla; return (r1, r2)) Hallofbla where it should (according to my goal) return no parse error but instead accept Hallo and allow the string parser to consume the rejected suffix but I will try to fix that. Matthias Hoermann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Requesting Feedback: I Love Haskell, but can't find a place to use it
Jonathan Geddes geddes.jonathan at gmail.com writes: I love Haskell. It is my absolute favorite language. But I have a very hard time finding places where I can actually use it! have you considered your head as such a place that should be easy to find. even just for specifying things, Haskell is tremendously useful. even if you don't write programs, but just their types. you can express your software design that way, and have it formally verified (by the compiler's type checker). best regards, J. W. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Requesting Feedback: I Love Haskell, but can't find a place to use it
On 31 May 2012 01:30, Jonathan Geddes geddes.jonat...@gmail.com wrote: I love Haskell. It is my absolute favorite language. But I have a very hard time finding places where I can actually use it! This has been bugging me for years and, like you, I think we ought to lean towards web-pages and mobile devices. Yesod has been a tremendous push forward in this direction but, as you already stated, the browser and android devices remain mostly unexplored in Haskell. Here's my bit: - There's a port of ghc for iphone. - There's frege (http://code.google.com/p/frege/), a non-strict, pure, functional programming language in the spirit of Haskell. - I've been working as a freelance developer for some time now. I focus on desktop apps in Haskell. I can't say I'm overwhelmed by the amount of offers (speaking of which, if anyone needs a freelance haskell developer,... ahem), but this area will not be clinically dead as long as we cannot use web applications knowing (99% sure) that the owner of the website cannot use our personal information for any purpose other than giving us our service. There's only two kinds of clients here, though: those that explicitly want Haskell, and those than don't care about the programming language. Otherwise, you'll have to sell Haskell and, personally, I'm not that good a salesman (10% success, tops). - I've also ported Haskell designs to other programming languages (with small adaptations). I only found this cost-effective because the code in Haskell was not going to be thrown away. Good luck. Please, let us know what you find. Cheers, Ivan. I had hoped that compiling Haskell to C with -fvia-C (or would it be just -C?) would allow Haskell to run in new, uncharted territory such as Android (with NDK), IOS, Google's NaCl, etc. But today I learned that GHC's C backend has been deprecated! Is it more difficult than I am imagining to get Haskell to work in these environments? Is it simply a matter of low interest in this kind of work? Or something more fundamental? Am I missing something? I'm hoping that the Haskell-JavaScript efforts will mature enough to make Haskell viable for client-side web apps. (I think the first sign of this will be a self-hosting Haskell-JavaScript compiler.) I use Haskell for Server-Side code with various web frameworks, but over the years more and more of the app logic is moved into client-side JavaScript, leaving the server-side code as little more than a simple validation and security layer over the database and other services. Haskell doesn't have any trouble with this, of course, but it's not exactly a role where it can shine. (Of course this is not true of ALL server-side code, just the kind of apps I have been writing.) So anyway I'd like to request feedback: where can I use Haskell besides simple CLI utilities, dull server code, or project Euler problems? Even if it's just to contribute to getting Haskell in the environments mentioned above, any feedback is welcome! Thanks for reading, --J Arthur ___ 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] Requesting Feedback: I Love Haskell, but can't find a place to use it
Thanks for the responses, everyone. J. W. wrote: have you considered your head as such a place that should be easy to find. even just for specifying things, Haskell is tremendously useful. even if you don't write programs, but just their types. you can express your software design that way, and have it formally verified (by the compiler's type checker). Yes! And in fact this is exactly how I use Haskell now (aside from little scripts and such). It has had a HUGE effect on the way I write software. There have been a number of times that a colleague has asked what a strange comment was in my Java[Script] code. When I tell them that the funny looking one-liner is the Haskell equivalent of the following 30+ Java[Script] lines, they are incredulous, to say the least. But taking that beautiful Haskell one-liner and manually transcribing it into an imperative language feels like being a human compiler. My favorite example of this was the use of the power set in JavaScript: //powerSet = filterM (const [True, False]) and then a few dozen JavaScript lines it compiled down to via the human compiler. --J Arthur On Thu, May 31, 2012 at 8:41 AM, Ivan Perez ivanperezdoming...@gmail.comwrote: On 31 May 2012 01:30, Jonathan Geddes geddes.jonat...@gmail.com wrote: I love Haskell. It is my absolute favorite language. But I have a very hard time finding places where I can actually use it! This has been bugging me for years and, like you, I think we ought to lean towards web-pages and mobile devices. Yesod has been a tremendous push forward in this direction but, as you already stated, the browser and android devices remain mostly unexplored in Haskell. Here's my bit: - There's a port of ghc for iphone. - There's frege (http://code.google.com/p/frege/), a non-strict, pure, functional programming language in the spirit of Haskell. - I've been working as a freelance developer for some time now. I focus on desktop apps in Haskell. I can't say I'm overwhelmed by the amount of offers (speaking of which, if anyone needs a freelance haskell developer,... ahem), but this area will not be clinically dead as long as we cannot use web applications knowing (99% sure) that the owner of the website cannot use our personal information for any purpose other than giving us our service. There's only two kinds of clients here, though: those that explicitly want Haskell, and those than don't care about the programming language. Otherwise, you'll have to sell Haskell and, personally, I'm not that good a salesman (10% success, tops). - I've also ported Haskell designs to other programming languages (with small adaptations). I only found this cost-effective because the code in Haskell was not going to be thrown away. Good luck. Please, let us know what you find. Cheers, Ivan. I had hoped that compiling Haskell to C with -fvia-C (or would it be just -C?) would allow Haskell to run in new, uncharted territory such as Android (with NDK), IOS, Google's NaCl, etc. But today I learned that GHC's C backend has been deprecated! Is it more difficult than I am imagining to get Haskell to work in these environments? Is it simply a matter of low interest in this kind of work? Or something more fundamental? Am I missing something? I'm hoping that the Haskell-JavaScript efforts will mature enough to make Haskell viable for client-side web apps. (I think the first sign of this will be a self-hosting Haskell-JavaScript compiler.) I use Haskell for Server-Side code with various web frameworks, but over the years more and more of the app logic is moved into client-side JavaScript, leaving the server-side code as little more than a simple validation and security layer over the database and other services. Haskell doesn't have any trouble with this, of course, but it's not exactly a role where it can shine. (Of course this is not true of ALL server-side code, just the kind of apps I have been writing.) So anyway I'd like to request feedback: where can I use Haskell besides simple CLI utilities, dull server code, or project Euler problems? Even if it's just to contribute to getting Haskell in the environments mentioned above, any feedback is welcome! Thanks for reading, --J Arthur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Confused by ghci output
*X 3^40 `mod` 3 == modexp2 3 40 3 False *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 I'm confused. Last I checked, 0 == 0. Using GHC 7.4.1, and the file x.hs (which has been loaded in ghci) can be found here: http://hpaste.org/69342 I noticed this after prop_sanemodexp was failing. Any help would be appreciated, - Clark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
Hi Clark, ghci is defaulting to Integer modexp2 forces Int Int overflows with 3^40 On 31/05/12 17:35, Clark Gaebel wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X fromInteger (3^40 `mod` 3) == modexp2 3 40 3 True *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 *X 3^40 `mod` 3 ::Int 2 I'm confused. Last I checked, 0 == 0. Int overflow is ugly! *X 3^40 12157665459056928801 *X maxBound :: Int 9223372036854775807 Claude Using GHC 7.4.1, and the file x.hs (which has been loaded in ghci) can be found here: http://hpaste.org/69342 I noticed this after prop_sanemodexp was failing. Any help would be appreciated, - Clark ___ 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] Confused by ghci output
Clark Gaebel cgae...@uwaterloo.ca wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 I'm confused. Last I checked, 0 == 0. This has to do with types: 3^40 `mod` 3 0 3^40 `mod` 3 :: Int 2 When doing number theory always use Integer. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife = sex) http://ertes.de/ signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
Hi Clark, On Thu, May 31, 2012 at 10:35 AM, Clark Gaebel cgae...@uwaterloo.ca wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 I'm confused. Last I checked, 0 == 0. Your HPaste shows the type of modexp2 is Int - Int - Int - Int, so ghci will infer that (3^40) is an Int. But an Int isn't big enough to hold 3^40. Prelude 3^40 :: Int -6289078614652622815 Prelude (3^40 :: Int) `mod` 3 2 Kevin -- Kevin Charter kevin.char...@acm.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
Wow, thanks! That was subtle. - Clark On Thu, May 31, 2012 at 12:49 PM, Claude Heiland-Allen cla...@goto10.orgwrote: Hi Clark, ghci is defaulting to Integer modexp2 forces Int Int overflows with 3^40 On 31/05/12 17:35, Clark Gaebel wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X fromInteger (3^40 `mod` 3) == modexp2 3 40 3 True *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 *X 3^40 `mod` 3 ::Int 2 I'm confused. Last I checked, 0 == 0. Int overflow is ugly! *X 3^40 12157665459056928801 *X maxBound :: Int 9223372036854775807 Claude Using GHC 7.4.1, and the file x.hs (which has been loaded in ghci) can be found here: http://hpaste.org/69342 I noticed this after prop_sanemodexp was failing. Any help would be appreciated, - Clark __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://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] Confused by ghci output
ghci 3^40 `mod` 3 :: Int 2 Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
On Thu, May 31, 2012 at 6:35 PM, Clark Gaebel wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 *X 3^40 `mod` 3 :: Int 1 *X 3^40 `mod` 3 :: Integer 0 I'm confused. Last I checked, 0 == 0. Yes, but 3^40 /= 3^40 when you have arithmetic overflow: *X 3^40 :: Int 689956897 *X 3^40 :: Integer 12157665459056928801 Regards, Sean ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
It looks like you are overflowing `Int` with 3^40. In your QuickCheck test, the function signature uses Int: prop_sanemodexp :: Int - Int - Int - Property Note: Prelude 3^40 12157665459056928801 Prelude 3^40 :: Int 689956897 Prelude 3^40 `mod` 3 0 Prelude (3^40 `mod` 3) :: Int 1 L. On Thu, May 31, 2012 at 5:35 PM, Clark Gaebel cgae...@uwaterloo.ca wrote: *X 3^40 `mod` 3 == modexp2 3 40 3 False *X modexp2 3 40 3 0 *X 3^40 `mod` 3 0 I'm confused. Last I checked, 0 == 0. Using GHC 7.4.1, and the file x.hs (which has been loaded in ghci) can be found here: http://hpaste.org/69342 I noticed this after prop_sanemodexp was failing. Any help would be appreciated, - Clark ___ 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] Confused by ghci output
The cafe is certainly responsive today! Thanks everyone - got it. Integer overflow ;) Regards, - Clark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Requesting Feedback: I Love Haskell, but can't find a place to use it
Besides our web app and batch pdf generation procedures, i use haskell for internal one-off tasks. Often i am being asked to import various data to database from text/excel files. Haskell is an excellent tool for this. On Wednesday, May 30, 2012 5:30:28 PM UTC-7, Jonathan Geddes wrote: I love Haskell. It is my absolute favorite language. But I have a very hard time finding places where I can actually use it! I had hoped that compiling Haskell to C with -fvia-C (or would it be just -C?) would allow Haskell to run in new, uncharted territory such as Android (with NDK), IOS, Google's NaCl, etc. But today I learned that GHC's C backend has been deprecated! Is it more difficult than I am imagining to get Haskell to work in these environments? Is it simply a matter of low interest in this kind of work? Or something more fundamental? Am I missing something? I'm hoping that the Haskell-JavaScript efforts will mature enough to make Haskell viable for client-side web apps. (I think the first sign of this will be a self-hosting Haskell-JavaScript compiler.) I use Haskell for Server-Side code with various web frameworks, but over the years more and more of the app logic is moved into client-side JavaScript, leaving the server-side code as little more than a simple validation and security layer over the database and other services. Haskell doesn't have any trouble with this, of course, but it's not exactly a role where it can shine. (Of course this is not true of ALL server-side code, just the kind of apps I have been writing.) So anyway I'd like to request feedback: where can I use Haskell besides simple CLI utilities, dull server code, or project Euler problems? Even if it's just to contribute to getting Haskell in the environments mentioned above, any feedback is welcome! Thanks for reading, --J Arthur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Need inputs for a Haskell awareness presentation
Hi folks, I have the opportunity to make a presentation to folks (developers and managers) in my organization about Haskell - and why it's important - and why it's the only way forward. I request you to share your experiences/suggestions for the following - 1. Any thoughts around the outline of the presentation - target audience being seasoned imperative programmers who love and live at the pinnacle of object oriented bliss. 2. Handling questions/comments like these in witty/interesting ways - a) It looks good and mathematical but practically, what can we do with it, all our stuff is in C++ b) Wow, what do you mean you cannot reason about its space complexity? c) Where's my inheritance? d) Debugging looks like a nightmare - we cannot even put a print in the function? e) Static types - in this day and age - come on - productivity in X is so much more - and that's because they got rid of type mess. f) Is there anything serious/large written in it? [GHC will not qualify as a good answer I feel] g) Oh FP, as in Lisp, oh, that's AI stuff right ... we don't really do AI. h) Any other questions/comments that you may have heard. 3. Ideas about interesting problems that can be used so that it appeals to people. I mean, while fibonacci etc look good but showing those examples tend to send the signal that it's good for those kind of problems. 4. Is talking about or referring to Lambda calculus a good idea - I mean, showing that using its ultra simple constructs one could build up things like if/then etc I'm gonna do my bit to wear the limestone!!! Regards, Kashyap ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need inputs for a Haskell awareness presentation
Regarding 2d, Debug.Trace is perfect for that. On Thu, May 31, 2012 at 2:23 PM, C K Kashyap ckkash...@gmail.com wrote: Hi folks, I have the opportunity to make a presentation to folks (developers and managers) in my organization about Haskell - and why it's important - and why it's the only way forward. I request you to share your experiences/suggestions for the following - 1. Any thoughts around the outline of the presentation - target audience being seasoned imperative programmers who love and live at the pinnacle of object oriented bliss. 2. Handling questions/comments like these in witty/interesting ways - a) It looks good and mathematical but practically, what can we do with it, all our stuff is in C++ b) Wow, what do you mean you cannot reason about its space complexity? c) Where's my inheritance? d) Debugging looks like a nightmare - we cannot even put a print in the function? e) Static types - in this day and age - come on - productivity in X is so much more - and that's because they got rid of type mess. f) Is there anything serious/large written in it? [GHC will not qualify as a good answer I feel] g) Oh FP, as in Lisp, oh, that's AI stuff right ... we don't really do AI. h) Any other questions/comments that you may have heard. 3. Ideas about interesting problems that can be used so that it appeals to people. I mean, while fibonacci etc look good but showing those examples tend to send the signal that it's good for those kind of problems. 4. Is talking about or referring to Lambda calculus a good idea - I mean, showing that using its ultra simple constructs one could build up things like if/then etc I'm gonna do my bit to wear the limestone!!! Regards, Kashyap ___ 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] Need inputs for a Haskell awareness presentation
On Thu, May 31, 2012 at 11:53 PM, C K Kashyap ckkash...@gmail.com wrote: Hi folks, I have the opportunity to make a presentation to folks (developers and managers) in my organization about Haskell - and why it's important - and why it's the only way forward. You (and we) may believe that but saying so usually does not work. What is more likely to work is talking to people about what interests them (rather than you :-) ). For example teachers of CS are usually struck by and bowled over by quicksort in 2 lines because for them teaching quicksort is considered an important activity. Professional object-oriented programmers are unlikely to take to such an 'academic' example kindly. Likewise those interested in algorithms and data-structures would be caught by a (tree) dfs in 1 line, or that a graph dfs and bfs are the same except that a [x] ++ pending becomes pending ++ [x] But if they were not so interested in algos and data-structures (Java programmers more than C++ are particularly prone to being using-happy, understanding-chary) this example would not work. So in short find what matters to your audience and then survey, focus and drill into that -- using Haskell I request you to share your experiences/suggestions for the following - 1. Any thoughts around the outline of the presentation - target audience being seasoned imperative programmers who love and live at the pinnacle of object oriented bliss. 2. Handling questions/comments like these in witty/interesting ways - a) It looks good and mathematical but practically, what can we do with it, all our stuff is in C++ b) Wow, what do you mean you cannot reason about its space complexity? c) Where's my inheritance? Yes you need to find a hot OO guru saying that inheritance is best avoided where templates/STL etc work d) Debugging looks like a nightmare - we cannot even put a print in the function? Maybe a (concocted) example of how the typechecker does most of the debugging for you? Better of course if the example is genuinely hacked out in front of the class (ideally from some thing they want to see solved) that can be convincing re things like debugging. This also brings up what is (for me) a very important point regarding haskell -- using an interpreter, ie ghci. -- the tight feedback loop -- not being bound to having to write a main -- the general sense of a workbench in which various objects (some joke here for the OO guys?) are are in different states of under construction to shrink-wrapped Personally I do not see how I could teach (or do) haskell without emacs. Admittedly this attracts some strongly and repels others equally strongly e) Static types - in this day and age - come on - productivity in X is so much more - and that's because they got rid of type mess. f) Is there anything serious/large written in it? [GHC will not qualify as a good answer I feel] g) Oh FP, as in Lisp, oh, that's AI stuff right ... we don't really do AI. h) Any other questions/comments that you may have heard. 3. Ideas about interesting problems that can be used so that it appeals to people. I mean, while fibonacci etc look good but showing those examples tend to send the signal that it's good for those kind of problems. 4. Is talking about or referring to Lambda calculus a good idea - I mean, showing that using its ultra simple constructs one could build up things like if/then etc I'm gonna do my bit to wear the limestone!!! Regards, Kashyap ___ 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] Need inputs for a Haskell awareness presentation
a) you can generate c++ with it :) (but don't tell it. it may be regarded as offense) b) - c) - d) stop debugging, you don't need it that much in haskell. But you need profiler. If they really want to print something in pure function you can show them function 'trace', from Debug.Trace e) I don't think that C++ people think that types are bad. If they do you can tell (beside the types don't let you mess up to much and stimulate clarity and documentation) about how easy is to do refactoring in typed language. f) You can show them Atom [1]. 5k Haskell code generates 20k C-code and it all works in real time in real trucks. Or Copilot. It's going to be used in airplanes. 4. I think it's bad idea. It's better to start with examples. What really strikes me about haskell is the simplicity of data types. I think the best way to start is to show Booleans, then lists, then Trees. It's so simple and beautiful You can say. Do you really need to know anything about syntax to understand this: data Bool = False | True or this data Time = Time Hour Minute Second or this data List a = Nil | Cons a (List a) and you can say that it is not built in. You can define it yourself and it works as fast as any other data type (or as slow). You can stress the idea of haskell data types is haskell UML. Don't show definitions just show them types like this: not :: Bool - Bool and :: Bool - Bool - Bool reverse :: [a] - [a] map :: (a - b) - [a] - [b] then you can show definitions and say about pattern matching. It is very intuitive. [1] http://hackage.haskell.org/package/atom ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Troubles understanding Parsec Error Handling
* Matthias Hörmann mhoerm...@gmail.com [2012-05-31 10:40:31+0200] I noticed there are still some other problems in the code. In particular it doesn't work as intended in cases like this one: parseTest (do; r1 - anyOf [Hello, Hallo, Foo, HallofFame]; r2 - string fbla; return (r1, r2)) Hallofbla where it should (according to my goal) return no parse error but instead accept Hallo and allow the string parser to consume the rejected suffix but I will try to fix that. This looks more like a job for regular expressions. E.g. using the regex-applicative package: let anyOf = foldr1 (|) . map string let re = (,) $ anyOf [Hello, Hallo, Foo, HallofFame] * string fbla Hallofbla =~ re Just (Hallo,fbla) Theoretically regular expressions also do the kind of optimization that you achieve with a trie, but this particular engine doesn't. Nevertheless, it may be a good base for your own engine. -- Roman I. Cheplyaka :: http://ro-che.info/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Requesting Feedback: I Love Haskell, but can't find a place to use it
It's difficult to imagine any kind of program that doesn't need testing; surely there is a role for Haskell in writing test data generators? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Most Important GHC extensions to learn/use?
Haskell Hackers,
I'm pretty comfortable with all of Haskell 98 (and 2010, really). But I've
always sort of avoided extensions. I realize that this is a bit silly and
if I want to continue learning, it probably means delving into the
extensions. Which ones are the most important to know from a practical
point of view? And which ones from a {Language,Category,Math}-theoretical
point of view? (Any other interesting/important points of view I'm missing?
:D )
As always, thanks for the feedback.
Cheers,
--J Arthur
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Re: [Haskell-cafe] Need inputs for a Haskell awareness presentation
On Fri, Jun 1, 2012 at 6:23 AM, C K Kashyap ckkash...@gmail.com wrote: Hi folks, I have the opportunity to make a presentation to folks (developers and managers) in my organization about Haskell - and why it's important - and why it's the only way forward. I request you to share your experiences/suggestions for the following - 1. Any thoughts around the outline of the presentation - target audience being seasoned imperative programmers who love and live at the pinnacle of object oriented bliss. Rustom nailed it. Take something imperative languages are really, really bad at and *show* how it's done in Haskell. * Parsing Haskell parser combinators make yacc look old school. By leveraging Haskell's DSL features, parsers often end up looking like the grammar they're implementing. Different parser combinator libraries let you do incremental input (Attoparsec), show clang-style diagnostics (Trifecta), or perform crazy optimizations automatically (uu-parsinglib). * Iteratee I/O encodeFile from to = mapOutput encode (sourceFile from) $$ sinkFile to It may not look like it, but the above function (using the conduit package) sets up a I/O pipeline that uses constant memory. There are HTTP, FTP, text encoding and parser libraries that can hook into the pipeline the same way. All the resources (sockets, file handles) tied up in the pipeline are finalized automatically when it finishes or when an exception is thrown. * Epic concurrency GHC comes with preemptive scheduling, STM and async I/O built in. Maybe you could demonstrate these with a ping-pong-style application. 2. Handling questions/comments like these in witty/interesting ways - a) It looks good and mathematical but practically, what can we do with it, all our stuff is in C++ Anything you can do in another Turing-complete language ;) Quite a few folks have helped push Haskell into the practical world, with useful things like web frameworks, ByteStrings, GUI bindings... It's suitable for practical applications already. b) Wow, what do you mean you cannot reason about its space complexity? That's not a bug, it's a feature! C++ gives you lots of control over how your program runs. Unfortunately, most people don't need that or don't know how to use it effectively. So most of the time, these low-level features just add a bunch of cruft with no real benefit to the programmer. Haskell goes the opposite way. The Haskell standard goes out of its way *not* to say how programs actually run -- only what the result should be. This lets the compiler optimize much more than in other languages. This philosophy is reflected in a common technique called stream fusion. I can't be bothered writing an example for this, but Google it and you'll find a few. c) Where's my inheritance? Right behind you ;) d) Debugging looks like a nightmare - we cannot even put a print in the function? Traditional debugging -- stepping through the program line by line -- fails miserably in Haskell, mostly due to (b). Haskell programmers tend to use more mathematical techniques: * Property-based testing, e.g. reverse (reverse xs) == xs. Used extensively in Xmonad. * Algebraic proofs (this works especially well for framework stuff like the MTL). * Sexy types: encoding invariants in the type so the compiler checks it for you. The fb (Facebook API) package does this with the NoAuth and Auth phantom types. For I/O-centric code, there's the traditional HUnit and HSpec. And as Clark said, there's always Debug.Trace. e) Static types - in this day and age - come on - productivity in X is so much more - and that's because they got rid of type mess. The designers of Haskell went out of their way to make sure 99% of types can be inferred by the compiler. It's good practice to put type annotations on things, but you don't have to. f) Is there anything serious/large written in it? [GHC will not qualify as a good answer I feel] * Yesod and Snap and Happstack -- all mature, well documented web frameworks. Yesod is the check-everything-at-compile-time one, Snap is the mix-and-match one and Happstack is the use-lots-of-combinators one. * Warp, a simple yet full-featured web server, trashes the competition in terms of performance -- yet consists of less than 1k lines of code. It uses all three of the techniques I mentioned above. * Xmonad is a window manager. I've used quite a few tiling window managers before, and Xmonad is the only one that hasn't crashed. * Geordi (http://www.eelis.net/geordi/), an IRC bot that compiles and runs C++ code, is written in Haskell. g) Oh FP, as in Lisp, oh, that's AI stuff right ... we don't really do AI. h) Any other questions/comments that you may have heard. 3. Ideas about interesting problems that can be used so that it appeals to people. I mean, while fibonacci etc look good but showing those examples tend to send the signal that it's good for those kind of problems.
Re: [Haskell-cafe] Fundeps and overlapping instances
Iavor Diatchki iavor.diatchki at gmail.com writes: Hello, the notion of a functional dependency is well established, and it was used well before it was introduced to Haskell (for example, take a look at http://en.wikipedia.org/wiki/Functional_dependency). So I'd be weary to redefine it lightly. Yes functional dependency is well established in relational algebra (set theory actually) -- it's about values in attributes. But there's nothing corresponding to typevars (I suppose you might call those patterns of values); there's nothing like overlaps. Perhaps instances with Fundeps should only use H98-style arguments? Perhaps we should disallow overlaps with Fundeps (as Hugs does pretty-much)? I can only understand tricky Fundeps by mentally translating them into type- level functions (and I was doing that before type families/associated types came along). class C a b| a - b=== type family CF a instance C a b === type instance CF a = b And that type instance is rejected because `b' is not in scope. Currently there are all sorts of tricks in instance declarations with overlaps and Fundeps, to achieve the effect of type-level functions. You do end up with instance arguments being all typevars, because the instance selection logic is really going on inside the constraints, with type-level 'helper functions'. Some of Oleg's instances are awesome (and almost impenetrable -- the TTypeable code is a tour de force). It's all so *dys-functional* (IMO). My take is that we should abandon Fundeps, and concentrate on introducing overlaps into type functions in a controlled way (what I've called 'dis- overlapped overlaps'.) AntC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Confused by ghci output
On 5/31/12 12:48 PM, Lorenzo Bolla wrote: It looks like you are overflowing `Int` with 3^40. In your QuickCheck test, the function signature uses Int: +1. I was bitten by this issue recently as well. When playing around with properties and debugging in GHCi, always beware of type defaulting to Integer. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Most Important GHC extensions to learn/use?
On 5/31/12 7:15 PM, Jonathan Geddes wrote:
Haskell Hackers,
I'm pretty comfortable with all of Haskell 98 (and 2010, really). But I've
always sort of avoided extensions. I realize that this is a bit silly and
if I want to continue learning, it probably means delving into the
extensions. Which ones are the most important to know from a practical
point of view? And which ones from a {Language,Category,Math}-theoretical
point of view? (Any other interesting/important points of view I'm missing?
:D )
There are a bunch which are mostly just syntax changes. The important
ones are:
ForeignFunctionInterface (aka FFI)
Not technically part of H98, though it was a quick addition. It
is part of H2010, so it's not really an extension anymore.
ScopedTypeVariables
This one's really easy, and in the cases where you want it you
really really want it.
KindSignatures
This one's simple, and it helps expose you to the idea of
kinds, which is helpful for what's to come.
TypeOperators
This one's trivial, but it makes things a bit prettier.
FlexibleContexts, FlexibleInstances
These are essential for actually using MPTCs (described below).
IMO they should be enabled automatically whenever MPTCs are on.
And there are also a bunch of ones about extending the deriving
mechanic to work with new classes or with newtypes.
Then there are the ones that actually change the language in a
significant way. I'd say the critical ones to learn are:
RankNTypes (or Rank2Types if you're squeamish)
This is used in lots of nice tricks like list fusion. Learning
list fusion is a good place for the H98 veteran to explore
next, since it's easy to pick up and has many applications
outside of just doing list fusion. Also, it's been around
forever and isn't going anywhere anytime soon.
MultiParamTypeClasses (aka MPTCs)
This has been around forever, and is considered standard
Haskell by most people, even though it hasn't made it into the
Report yet (due the the fundeps vs TFs issue).
FunctionalDependencies (aka fundeps)
This is helpful for making certain MPTCs usable without too
many type signatures. Also, it's good for understanding the
fundeps vs TFs issue. Also, this one has been around forever,
and although it's fallen into disfavor it is still
indispensable due to limitations in TFs.
TypeFamilies (aka TFs)
These are really nifty and they're all the rage these days. In
a formal sense they're equivalent to fundeps, but in practice
they're weaker than fundeps.
GADTs
These are really nifty and they're all the rage these days.
Though beware, GADTs are a rabbit hole leading off to the world
of dependent types. You should be aware of the basic ideas
here, though don't worry too much about the theory (unless you
want to spend a lot of time worrying about the theory).
--
Live well,
~wren
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Re: [Haskell-cafe] Most Important GHC extensions to learn/use?
Thanks, Wren, I really appreciate the detailed response! Though I am
surprised that Template Haskell isn't on your list. From the little I know
of TH it seems like all of the interesting generic/generative stuff is done
with TH. Do the other extensions subsume the need for TH, or is it just not
terribly interesting?
--J Arthur
On Thu, May 31, 2012 at 10:29 PM, wren ng thornton w...@freegeek.orgwrote:
On 5/31/12 7:15 PM, Jonathan Geddes wrote:
Haskell Hackers,
I'm pretty comfortable with all of Haskell 98 (and 2010, really). But I've
always sort of avoided extensions. I realize that this is a bit silly and
if I want to continue learning, it probably means delving into the
extensions. Which ones are the most important to know from a practical
point of view? And which ones from a {Language,Category,Math}-**
theoretical
point of view? (Any other interesting/important points of view I'm
missing?
:D )
There are a bunch which are mostly just syntax changes. The important ones
are:
ForeignFunctionInterface (aka FFI)
Not technically part of H98, though it was a quick addition. It
is part of H2010, so it's not really an extension anymore.
ScopedTypeVariables
This one's really easy, and in the cases where you want it you
really really want it.
KindSignatures
This one's simple, and it helps expose you to the idea of
kinds, which is helpful for what's to come.
TypeOperators
This one's trivial, but it makes things a bit prettier.
FlexibleContexts, FlexibleInstances
These are essential for actually using MPTCs (described below).
IMO they should be enabled automatically whenever MPTCs are on.
And there are also a bunch of ones about extending the deriving mechanic
to work with new classes or with newtypes.
Then there are the ones that actually change the language in a significant
way. I'd say the critical ones to learn are:
RankNTypes (or Rank2Types if you're squeamish)
This is used in lots of nice tricks like list fusion. Learning
list fusion is a good place for the H98 veteran to explore
next, since it's easy to pick up and has many applications
outside of just doing list fusion. Also, it's been around
forever and isn't going anywhere anytime soon.
MultiParamTypeClasses (aka MPTCs)
This has been around forever, and is considered standard
Haskell by most people, even though it hasn't made it into the
Report yet (due the the fundeps vs TFs issue).
FunctionalDependencies (aka fundeps)
This is helpful for making certain MPTCs usable without too
many type signatures. Also, it's good for understanding the
fundeps vs TFs issue. Also, this one has been around forever,
and although it's fallen into disfavor it is still
indispensable due to limitations in TFs.
TypeFamilies (aka TFs)
These are really nifty and they're all the rage these days. In
a formal sense they're equivalent to fundeps, but in practice
they're weaker than fundeps.
GADTs
These are really nifty and they're all the rage these days.
Though beware, GADTs are a rabbit hole leading off to the world
of dependent types. You should be aware of the basic ideas
here, though don't worry too much about the theory (unless you
want to spend a lot of time worrying about the theory).
--
Live well,
~wren
__**_
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