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Learning Haskell - Thu, 03/12/2015 - 4:59pm
Categories: Offsite Blogs

Haskell in Emacs - Thu, 03/12/2015 - 4:24pm
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Haskell in Emacs - Thu, 03/12/2015 - 4:24pm
Categories: Offsite Blogs

Monadic/sequential migration implementation for datain acid-state

haskell-cafe - Thu, 03/12/2015 - 3:28pm
Full description of my problem is on Stack Overflow: Any comments or suggestions would be greatly appreciated! _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
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Learning Haskell - Thu, 03/12/2015 - 12:49pm
Categories: Offsite Blogs

Bad recursion? When can something be on both sidesof an equation?

haskell-cafe - Thu, 03/12/2015 - 8:49am
Dear Haskellers, In another thread [1], I talked about computing what I've been lately calling the "total descendents" of a subset S of a graph: that is, the set of nodes t for which every maximal sequence of predecessors intersects S. I got it done, functionally [2]. But in the process I wrote something that hangs, and I can't figure out why. The problem arose in the following passage. (Glab stands for Graph Label, a synonym for Int.) totalDescendents :: S.Set Glab -> Graph -> S.Set Glab totalDescendents roots graph = b where (a,b,c,graph) = totalDescendentsCtrlr -- tricky (roots, S.empty, M.empty, graph) totalDescendentsCtrlr :: TotalDescendentsData -> TotalDescendentsData totalDescendentsCtrlr (a,b,c,gr) = if S.null a' -- fails, as does a == a' -- a == a' is one iteration slower but should have same effect then (a',b',c',gr') else totalDescendentsCtrlr (a',b',c',gr') where (a',b',c',gr') = visi
Categories: Offsite Discussion

Theory Lunch (Institute of Cybernetics, Tallinn): Limit languages of cellular automata

Planet Haskell - Thu, 03/12/2015 - 8:32am

At today’s Theory Lunch I discussed limit languages of cellular automata, and Lyman Hurd’s example of a CA whose limit language is not regular. I wrote about this on my other blog.


Categories: Offsite Blogs

TH not compiling when writing the code directly does

haskell-cafe - Thu, 03/12/2015 - 7:07am
I’m stuck getting a TH expansion to compile. When I take the generated code and compile it directly, it is fine. But when expanding and compiling, it fails. The problem seems related to instanceD, where I provide the type as: (appT (appT (conT devName') (varT $ mkName "Word8")) (varT $ mkName "BV”)) which expands to: IDENTIFICATION__MODEL_ID Word8 BV No matter what I put for the second type (BV), it generates the compile error. For example, Word8 or Word16 gives the same error. But if I take the resulting expression and just put it into the file and compile, it compiles fine. So something about expansion is causing the problem. Is there some more correct way to make the expression rather than nesting two appT? Any ideas? Note: the generation of the functions with (map (\f -> returnQ f) (concat funs)) is ugly in my opinion. I could not find the right way to express this. So all ideas welcome. Mike GEN DEC -------------- makeInstance :: String -> [String] -> Q [Dec] makeInstance devName regNam
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David Turner quote on lisp and FP

haskell-cafe - Thu, 03/12/2015 - 5:57am
There is this quote: *It needs to be said very firmly that LISP is not a functional language at all. My suspicion is that the success of Lisp set back the development of a properly functional style of programming by at least ten years.* David Turner found here and there on the net eg Does anyone have/know the original reference? Thanks Rusi
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Needs some help walking out of HarmTrace's Cabal Hell

Haskell on Reddit - Thu, 03/12/2015 - 1:35am

Hey r/haskell, so I got introduced to haskell a couple weeks ago trying to use a really cool music analysis hackage chordify is using. I love the language, but didn't expect cabal hell would be this bad. If anyone could help me figure out how to get HarmTrace's dependency resolved, I would be eternally thankful.


submitted by pickledchickenfoot
[link] [6 comments]
Categories: Incoming News

Mathematical functions with multiple arguments

haskell-cafe - Wed, 03/11/2015 - 10:45pm
Hi everybody, I have a function of type plot :: ([Double] -> Double) -- A function to plot -> [(Double, Double)] -- Range for all arguments -> IO () I want to enforce the fact that ranges for all arguments should be provided. Is there a way to make the type system enforce it?
Categories: Offsite Discussion

My first big Haskell project

Haskell on Reddit - Wed, 03/11/2015 - 8:54pm

Hey guys,

I was just looking back at my first big Haskell project, which you can find here:

It's a small "A.I." which creates music through a genetic algorithms. I put a couple of the tunes it made at various points online at ( plus one now as a "restart", be careful of your years on the earliest ones!).

Looking back on this code, it's a bit embarrassing now, so I was wondering, what have you guys learnt looking back at your first big projects?

submitted by julek1024
[link] [17 comments]
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What imperative languages do Haskellers like?

Haskell on Reddit - Wed, 03/11/2015 - 6:24pm

Now that I've been using Haskell for almost a year I find going back to imperative languages incredibly frustrating. I went and brushed up on my Python and the biggest problem I had with it was how verbose it is (which frustrated me more than the lack of compile time optimisation or type safety...).

For various reasons I'm finding JavaScript to be quite nice. The syntax is reasonably lean, there are higher order functions and I can take lessons from Haskell about mutable state. Duck Typing is annoying, as is the lack of compile time assurance and the largely poor performance. I certainly wouldn't do anything more than client side functionality for web.

I realise that what I'm really liking about Haskell more than anything is how terse it is. Once you understand the syntax it's not just quick to write but it's easy to understand.

I've seen a bit of J around and it looks like it might push that a bit far. Anyone have any experience with it? Once you understand the syntax is it possible to decipher what someone else's code means or is it a "write only language"?

What imperative languages do Haskellers out there like?

submitted by TheCriticalSkeptic
[link] [84 comments]
Categories: Incoming News