[Haskell-cafe] Trouble installing leksah

I now have the Haskell platform install problem solved but I'm now trying to get the leksah IDE installed and I'm getting this. runhaskell Setup configure Configuring leksah-0.6.1... Setup: At least the following dependencies are missing: glib >=0.10, gtk >=0.10, gtksourceview2 >=0.10.0 I am awa

Re: [Haskell-cafe] Trouble installing leksah

On Thu, Sep 17, 2009 at 9:01 AM, Gregory Propf wrote: > > I now have the Haskell platform install problem solved but I'm now trying to > get the leksah IDE installed and I'm getting this. > > runhaskell Setup configure > Configuring leksah-0.6.1... > Setup: At least the following dependencies are

Re: [Haskell-cafe] GHC threaded runtimes and pure functions

Bulat Ziganshin wrote: Hello Andrew, Wednesday, September 16, 2009, 11:31:22 PM, you wrote: If you're going to use par, it doesn't really matter how many sparks you create. You just need to avoid creating millions of really tiny sparks. You could create, say, eight and let GHC figure out th

[Haskell-cafe] Where can I find a non-fee-based version of Hudak's paper, "Conception, evolution, and application of functional programming languages"?

Does anybody know where I can find a non-fee-based version of Paul Hudak's paper, "Conception, evolution, and application of functional programming languages" [1]? There used to be a version that did not require an ACM account available at http://www.cs.berkeley.edu/~jcondit/pl-prelim/hudak89funct

[Haskell-cafe] Suggested additions to System.FilePath.Posix/Windows

Hello Neil I used System.FilePath.Posix quite extensively recently, and I thank you for the package filepath. There were however two words that I needed which I could not construct from those in System.FilePath.Posix. They are maybe of interest to you and others. I submit these two words to you

[Haskell-cafe] Re: Question about haskell.cs.yale.edu/

Today I received the request below. At first the URL confused me, but apparently www.haskell.org is known under two names :-) The request should probably be handled by someone involved in ICFP. /M On Wed, Sep 16, 2009 at 11:53 PM, Peter Green wrote: > Hi, > > I was wondering whether you would

[Haskell-cafe] ANNOUNCE: graphviz-2999.5.1.0

I'm pleased to announce version 2999.5.1.0 [1] of the graphviz library, which provides bindings to the GraphViz [2] suite of tools for drawing graphs. [1] http://hackage.haskell.org/package/graphviz-2999.5.1.0 [2] http://www.graphviz.org/ This is mainly a bug-fix release; as such, there is no API

Re: [Haskell-cafe] Trouble installing leksah

There's no such named package in Hackage though.  That was the first thing I looked for.  All Hackage has with the string "gtk2hs" is this stuff gtk2hs-cast-glade library: A type class for cast functions of Gtk2hs: glade packagegtk2hs-cast-glib library: A type class for cast functions of Gtk2hs:

Re: [Haskell-cafe] Trouble installing leksah

Am Donnerstag 17 September 2009 12:35:19 schrieb Gregory Propf: > There's no such named package in Hackage though.  That was the first thing > I looked for.  All Hackage has with the string "gtk2hs" is this stuff AFAIK, gtk2hs is not yet cabalized and not on Hackage, look at http://haskell.org/gt

[Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Hi all. This email is in literate Haskell; you should be able to load it into ghci and verify what I'm saying (nb: it won't compile without alteration: see below). I'm trying to do something which may anyway be stupid / not the best approach to what I'm trying to achieve; however, it's not worki

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Hey Andy, On Thu, Sep 17, 2009 at 15:40, Andy Gimblett wrote: > > Now, some of those algebraic data type types happen to be > enumerations; in this case, my idea is to list the constructors, with > the rule that each constructor's position in the list is the Int which > gets converted into that

Re: [Haskell-cafe] How to understand the 'forall' ?

On Thu, Sep 17, 2009 at 8:36 AM, Ryan Ingram wrote: > ... > Explicitly: > > Haskell: >> test1 :: forall a. a -> Int >> test1 _ = 1 >> test2 :: (forall a. a) -> Int >> test2 x = x > > explicitly in System F: > > test1 = /\a \(x :: a). 1 > test2 = \(x :: forall a. a). x @Int > > /\ is type-level lam

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Am Donnerstag 17 September 2009 15:56:03 schrieb José Pedro Magalhães: > Hey Andy, > > On Thu, Sep 17, 2009 at 15:40, Andy Gimblett wrote: > > Now, some of those algebraic data type types happen to be > > enumerations; in this case, my idea is to list the constructors, with > > the rule that each

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Hello, On Thu, Sep 17, 2009 at 16:05, Daniel Fischer wrote: > Am Donnerstag 17 September 2009 15:56:03 schrieb José Pedro Magalhães: > > Hey Andy, > > > > On Thu, Sep 17, 2009 at 15:40, Andy Gimblett > wrote: > > > Now, some of those algebraic data type types happen to be > > > enumerations; in

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

On 17 Sep 2009, at 15:21, José Pedro Magalhães wrote: > > E.g. here's a type Bar with three constructors: > > > data Bar = X | Y | Z deriving (Show) > > > instance Enumerated Bar where > > > constructors = [X, Y, Z] > > > > (This is certainly ugly. Any suggestions?) > > > |constructors| is

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Am Donnerstag 17 September 2009 16:30:14 schrieb Andy Gimblett: > On 17 Sep 2009, at 15:21, José Pedro Magalhães wrote: > > > > E.g. here's a type Bar with three constructors: > > > > > data Bar = X | Y | Z deriving (Show) > > > > > instance Enumerated Bar where > > > > > constructors = [X, Y,

[Haskell-cafe] Re: [Haskell-beginners] map question

Remember that there is asymmetry between (+) and (-).  The former has the commutative property and the latter does not so: (+) 3 4 = 7 and (+) 4 3 = 7 but (-) 3 4 = -1 and (-) 4 3 = 1 --- On Thu, 9/17/09, Tom Doris wrote: From: Tom Doris Subject: Re: [Haskell-beginners] map question To

[Haskell-cafe] Re: Where can I find a non-fee-based version of Hudak's paper, "Conception, evolution, and application of functional programming languages"?

> Does anybody know where I can find a non-fee-based version of Paul > Hudak's paper, "Conception, evolution, and application of functional > programming languages" [1]? There used to be a version that did not seems you can get a djvu copy here http://lib.org.by/info/Cs_Computer science/CsPl_Pro

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Am Donnerstag 17 September 2009 15:40:10 schrieb Andy Gimblett: > > > instance (Enumerated a) => Target a where > > convert n | n `elem` [0..len-1] = Just $ constructors !! n > > > > | otherwise = Nothing > > > > where len = length constructors Yes, the second appe

Re: [Haskell-cafe] Where can I find a non-fee-based version of Hudak's paper, "Conception, evolution, and application of functional programming languages"?

On 2009-09-17, at 1:41 AM, Benjamin L.Russell wrote: Does anybody know where I can find a non-fee-based version of Paul Hudak's paper, "Conception, evolution, and application of functional programming languages" [1]? When in doubt, check citeseer. http://citeseerx.ist.psu.edu/viewdoc/summary?d

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

On 17 Sep 2009, at 16:50, Daniel Fischer wrote: Yes, the second appearance of 'constructors' is at an unspecified type. instance (Enumerated a) => Target a where convert n | n < 0 = Nothing | otherwise = case drop n constructors of (x:_) -> Just x

Re: [Haskell-cafe] Re: [Haskell-beginners] map question

(-) happens to be the only prefix operator in haskell, it also an infix operator. so: > 4 - 2 2 > -3 -3 > ((-) 5) 3 -- note that in this case (-) is treated like any regular function so 5 is the first parameter 2 > (5 - ) 3 2 > (-5 ) -5 > (flip (-) 5) 3 -2 It's a little wart brought about by th

Re: [Haskell-cafe] Re: [Haskell-beginners] map question

> 2009/9/17 Joost Kremers >> >> Hi all, >> >> I've just started learning Haskell and while experimenting with map a bit, I >> ran >> into something I don't understand. The following commands do what I'd expect: >> >> Prelude> map (+ 1) [1,2,3,4] >> [2,3,4,5] >> Prelude> map (* 2) [1,2,3,4] >> [2,

Re: [Haskell-cafe] How to understand the 'forall' ?

On Thu, Sep 17, 2009 at 6:59 AM, Cristiano Paris wrote: > On Thu, Sep 17, 2009 at 8:36 AM, Ryan Ingram wrote: > > ... > > Explicitly: > > > > Haskell: > >> test1 :: forall a. a -> Int > >> test1 _ = 1 > >> test2 :: (forall a. a) -> Int > >> test2 x = x > > > > explicitly in System F: > > > > tes

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Am Donnerstag 17 September 2009 18:01:36 schrieb Andy Gimblett: > On 17 Sep 2009, at 16:50, Daniel Fischer wrote: > > Yes, the second appearance of 'constructors' is at an unspecified > > type. > > > > instance (Enumerated a) => Target a where > >convert n > > > > | n < 0 = Nothing >

Re: [Haskell-cafe] Ambiguous type variable with subclass instance (also: is there a better way to do this?)

Here's a way that works more closely to your original version: instance Enumerated a => Target a where convert n | n >= 0 && n < numConstrs = Just (constrs !! n) | otherwise = Nothing where constrs = constructors numConstrs = length constrs Alternatively: insta

Re: [Haskell-cafe] weak pointers and memoization (was Re: memoization)

What are you trying to use this for? It seems to me that for memo tables you almost never have references to they keys outside the lookup table since the keys are usually computed right at the last minute, and then discarded (otherwise it might be easier to just cache stuff outside the function).

[Haskell-cafe] Peano axioms

Hi, Below are two attempts to define Peano arithmetic in Haskell. The first attempt, Peano1, consists of just a signature in the class with the axioms in the instance. In the second attempt, Peano2, I am trying to move the axioms into the class. The reason is, I want to put as much specification as

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

On Tue, Sep 15, 2009 at 11:31 PM, Daniel Fischer wrote: > ... > Yeah, you do *not* want the whole file to be read here, except above for > testing purposes. That's not true. Sometimes I want to, sometimes don't. But I want to use the same code for reading files and exploit laziness to avoid read

Re: [Haskell-cafe] Peano axioms

The problem is that you are using 'suc' as if it is a constructor: ((suc m) `eq` (suc n) = m `eq` n) You'll have to change it to something else, and it will probably require adding an unpacking function to your class and it will probably be messy. I'd suggest you make use of the Eq typeclass and d

[Haskell-cafe] Composition, delegation and interfaces -- a 20K ft critique of Noop

Dear Programmers, Someone just asked me to give my opinion on Noop's composition proposal. It reminds me a little bit of Selfwhich found its way into JavaScript. It also reminds

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

Am Donnerstag 17 September 2009 21:07:28 schrieb Cristiano Paris: > On Tue, Sep 15, 2009 at 11:31 PM, Daniel Fischer > > wrote: > > ... > > Yeah, you do *not* want the whole file to be read here, except above for > > testing purposes. > > That's not true. Sometimes I want to, sometimes don't. The

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

On Thu, Sep 17, 2009 at 10:01 PM, Daniel Fischer wrote: > ... > readBit fn = do >    txt <- readFile fn >    let (l,_:bdy) = span (/= '\n') txt >    return $ Bit (read l) bdy > > ? > > With > > main = do >    args <- getArgs >    let n = case args of >                (a:_) -> read a >            

Re: [Haskell-cafe] algebra/grammar/language for expressing time intervals

Iain Alexander wrote: You might want to take a look at RFC 2445 Internet Calendaring and Scheduling Core Object Specification Section 4.8.5.4 Recurrence Rule Another source of inspiration might be the syntax used in remind[1]. /M [1]: http://www.roaringpenguin.com/products/remind -- Magnus T

Re: [Haskell-cafe] Peano axioms

I don't understand your goal. Isn't Peano arithmetic summarized in Haskell as: data Peano = Zero | Succ Peano deriving Eq This corresponds to a first-order logic over a signature that has equality, a constant symbol 0, and a one-place successor function symbol S. Function symbols such as < and

[Haskell-cafe] ANN: Unification in a Commutative Monoid (cmu 1.1) and a new release of Abelian group unification and matching (agum 2.2)

Package cmu 1.1 provides unification in a commutative monoid, also know as ACU-unification. The core computation finds the minimal non-zero solutions to homogeneous linear Diaphantine equations. The linear equation solver has been place in a separate module so it can be used for other application

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

Am Donnerstag 17 September 2009 22:20:55 schrieb Cristiano Paris: > On Thu, Sep 17, 2009 at 10:01 PM, Daniel Fischer > > wrote: > > ... > > readBit fn = do > >    txt <- readFile fn > >    let (l,_:bdy) = span (/= '\n') txt > >    return $ Bit (read l) bdy > > > > ? > > > > With > > > > main = do

[Haskell-cafe] help with FFI

Hello Lets say I have a library in C with a header like this: #include /*really big structure*/ typedef struct { int *a; int *b; /*lots of stuff ... */ int *z; } foo; /*this function allocate memory and fill the structure, reading from a file*/ int create_foo(foo *f,FILE *file,int x,int y); /

Re: [Haskell-cafe] weak pointers and memoization (was Re: memoization)

In my case, the results of each computation are used to generate a node in a graph structure (dag). The key, oddly, is a hash of a two-tuple that gets stored in the data structure after the computation of the node finishes. If I don't memoize the function to build a node, the cost of generating t

[Haskell-cafe] Re: help with FFI

typedef struct { int *a; int *b; /*lots of stuff ... */ int *z; } foo; int create_foo(foo *f,FILE *file,int x,int y); int use_foo(foo *f,int w); int destroy_foo(foo *f); newtype Foo = Foo () foreign import ccall "static foo.h create_foo" c_create_foo :: Ptr (Foo) -> Ptr (CFile) -> CInt -> CInt

[Haskell-cafe] About the parse error (possibly incorrect indentation)

Hi, I am trying to get the function showMinProp to return String, but I always get an error of parse error (possibly incorrect indentation) Who can help with this? any idea? Thank u in advance! data Prop = Var String | Negation Prop | BinOp Op Prop Prop data Op = And | Or | Implies | Equiv

Re: [Haskell-cafe] About the parse error (possibly incorrect indentation)

Am Freitag 18 September 2009 02:17:22 schrieb xu zhang: > showMinProp :: Int -> Prop -> String > showMinProp preNo (BinOp op p q) = >        case op of >          And -> let a = 4 >          Or  -> let a = 3 >          Implies -> let a = 2 >          Equiv   -> let a = 1 >        if (a > preNo) >  

Re: [Haskell-cafe] How to understand the 'forall' ?

Cristiano Paris wrote: On Wed, Sep 16, 2009 at 7:12 PM, Ryan Ingram wrote: Here's the difference between these two types: test1 :: forall a. a -> Int -- The caller of test1 determines the type for test1 test2 :: (forall a. a) -> Int -- The internals of test2 determines what type, or types, to

[Haskell-cafe] ∀ lexing in ghc and ghci

Hi, I'm getting different behavior in ghci and ghc with the identifier ∀. In ghc I need to wrap it with parens, as in > (∀) :: Var -> Base -> Formula -> Formula > (∀) = All In ghci, I get an error this way Formula.lhs:112:2: Invalid type signature In ghci I can do > ∀ :: Var -> Base ->

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Am Freitag 18 September 2009 03:31:13 schrieb Sean McLaughlin: > Hi, > I'm getting different behavior in ghci and ghc with the identifier ∀. In > ghc I need > to wrap it with parens, as in > > > (∀) :: Var -> Base -> Formula -> Formula > > (∀) = All > > In ghci, I get an error this way > > Formu

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Hi Daniel, Would you try putting that in a file and loading it in ghci? Your example also works for me. Prelude> let (∀) = 5 Prelude> (∀) 5 Sean On Thu, Sep 17, 2009 at 9:41 PM, Daniel Fischer wrote: > Am Freitag 18 September 2009 03:31:13 schrieb Sean McLaughlin: > > Hi, > > I'm getting d

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Am Freitag 18 September 2009 03:51:40 schrieb Sean McLaughlin: > Hi Daniel, > Would you try putting that in a file and loading it in ghci? Your > example also works for me. > > Prelude> let (∀) = 5 > Prelude> (∀) > 5 > > Sean Sure: da...@linux-mkk1:~/Haskell/CafeTesting> cat Forall.hs module Fo

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

I am confused about why this thread is talking about unsafePerformIO at all. It seems like everything you all want to do can be accomplished with the much less evil unsafeInterleaveIO instead. (Which is still a bit evil; but it's the difference between stealing cookies from the cookie jar and com

Re: [Haskell-cafe] Re: [Haskell-beginners] map question

Heh, perhaps we should petition to have a new computer key and symbol added to the world's way of writing maths, something like maybe a downward angled slash to mean prefix (-) :) --- On Thu, 9/17/09, Job Vranish wrote: From: Job Vranish Subject: Re: [Haskell-cafe] Re: [Haskell-beginners] m

[Haskell-cafe] Re: Where can I find a non-fee-based version of Hudak's paper, "Conception, evolution, and application of functional programming languages"?

On Thu, 17 Sep 2009 08:55:19 -0700, John Melesky wrote: >On 2009-09-17, at 1:41 AM, Benjamin L.Russell wrote: >> Does anybody know where I can find a non-fee-based version of Paul >> Hudak's paper, "Conception, evolution, and application of functional >> programming languages" [1]? > >When in dou

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Weird. OK, thanks a lot! I'm switching to ¥ until I get this figured out. Sean On Thu, Sep 17, 2009 at 10:00 PM, Daniel Fischer wrote: > Am Freitag 18 September 2009 03:51:40 schrieb Sean McLaughlin: > > Hi Daniel, > > Would you try putting that in a file and loading it in ghci? Your > > ex

[Haskell-cafe] code-build-test cycle

I'm working on a GUI application in qtHaskell, and I have a bit of a bind. Using ghci, it launches quickly but runs slowly. On the other hand, compiling (mainly linking) takes a while---several minutes. The truth is that I can compile it much faster if I selectively import the needed modules, s

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Am Friday 18 September 2009 04:41:13 schrieben Sie: > Weird. OK, thanks a lot! I'm switching to ¥ until I get this figured > out. Sean > What does your ghci say for Data.Char.isSymbol (toEnum 8704) ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell

Re: [Haskell-cafe] Is it safe to use unsafePerformIO here?

Am Freitag 18 September 2009 04:06:11 schrieb Ryan Ingram: > I am confused about why this thread is talking about unsafePerformIO at > all.  It seems like everything you all want to do can be accomplished with > the much less evil unsafeInterleaveIO instead.  (Which is still a bit evil; > but it's

Re: [Haskell-cafe] code-build-test cycle

Am Freitag 18 September 2009 04:42:32 schrieb Michael Mossey: > I'm working on a GUI application in qtHaskell, and I have a bit of a bind. > Using ghci, it launches quickly but runs slowly. On the other hand, > compiling (mainly linking) takes a while---several minutes. The truth is Is the library

Re: [Haskell-cafe] About the parse error (possibly incorrect indentation)

On Sep 17, 2009, at 20:17 , xu zhang wrote: case op of And -> let a = 4 Or -> let a = 3 Implies -> let a = 2 Equiv -> let a = 1 "let" isn't an assignment command, it's a scoping command. That is, > let a = 3 in ... is equivalent to something lik

Re: [Haskell-cafe] code-build-test cycle

Hello Michael, Friday, September 18, 2009, 6:42:32 AM, you wrote: > Now I'm wondering if Hugs is a faster interpreter. 2x slower, and incompatib;e with qtHaskell > meaningful way without compilation. Any advice welcome. Maybe there is a > way to speed up the interpretation. if compilation is f

Re: [Haskell-cafe] ∀ lexing in ghc and ghci

Daniel Fischer writes: >> In ghci I can do >> >> > ∀ :: Var -> Base -> Formula -> Formula >> > ∀ = All >> >> fine. But then ghc complains. What's going on here? > Maybe your encodings aren't UTF8? Or rather, one of them is UTF-8, and the other isn't. So that in one case, you get the 'forall'

Re: [Haskell-cafe] Re: [Haskell-beginners] map question

Gregory Propf writes: > Heh, perhaps we should petition to have a new computer key and symbol > added to the world's way of writing maths, something like maybe a > downward angled slash to mean prefix (-) Or just use 'negate' and 'subtract'? -k -- If I haven't seen further, it is by standing

[Haskell-cafe] Re: Where can I find a non-fee-based version of Hudak's paper, "Conception, evolution, and application of functional programming languages"?

On Thu, 17 Sep 2009 15:32:51 + (GMT), jean legrand wrote: >> Does anybody know where I can find a non-fee-based version of Paul >> Hudak's paper, "Conception, evolution, and application of functional >> programming languages" [1]? There used to be a version that did not > >seems you can get