- Haskell-Cafe - Haskell.org

Diony Rosa
by Diony Rosa 01 Sep '14

01 Sep '14

http://www.sarah-aloisi.com/ftpkk/lbqwswuvjc.ocrjttewxqiidnzuutwvyhq

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cabal sdist and auto-generated modules
by Marios Titas 31 Aug '14

31 Aug '14

I am trying to run cabal sdist on a package where one of exposed modules does not exists because it is automatically generated by setup.hs. cabal refuses to do that because it cannot find the file corresponding to that module. Is there a solution to that problem? The package builds just fine.

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RTS options to control name of eventlog file.
by Serguey Zefirov 31 Aug '14

31 Aug '14

Is there any? Because when running and profiling two same programs they will write into same eventlog file. Not a good situation.

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[ANN] igrf-0.2
by Douglas McClean 31 Aug '14

31 Aug '14

igrf is a library that provides an implementation of the International Geomagnetic Reference Field, which is just what it sounds like. I've tested it against NOAA's online calculator, but use it at your own risk. Note that the input is in geocentric and not geodetic coordinates. There is haddock documentation, I'm working on figuring out why it isn't on hackage and how to fix it. -Doug McClean

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Monads vs Linear regions
by Timotej Tomandl 30 Aug '14

30 Aug '14

How do they compare? Can Linear regions handle all uses of monads or does they lack some applications?

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Fwd: Linear regions ("Linear Regions Are All You Need") as the only way of encapsulation of impure state
by Timotej Tomandl 30 Aug '14

30 Aug '14

I was thinking for a while about if other kinds of handling of impure state have any advantages over linear regions. So I thought it will be nice to open the discussion about how does it compare with monads, linear types, uniqueness typing and monadic regions.

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[ANN] codex 0.1.0.4
by Alois Cochard 30 Aug '14

30 Aug '14

Hi Cafe, I just wanted to let you know that I have just released a new version of `codex` on hackage. There is *no new features* in this version, but thanks for the help from Hubert Behaghel I was able to investigate issues with MacOS. So basically this version now work with MacOS, if you had give a try before please delete your "~/.codex" configuration file before installing the new version. Cheers -- *Λ\ois* http://twitter.com/aloiscochard http://github.com/aloiscochard

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ICFP pre-party
by Roman Cheplyaka 30 Aug '14

30 Aug '14

We're having a small unofficial ICFP pre-party today in Gothenburg. All haskell-cafe readers that happen to be in Gothenburg are welcome :-) The plan is to meet at The Bishop's Arms (Kungsportsavenyen 36) at 19.00. NOTE: there are three Bishop's Arms in Gothenburg, so mind the address. Feel free to text me at +380662285780. Roman

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Re: [Haskell-cafe] Using 'lens' for "over"-like computation in Monad
by Nikolay Amiantov 30 Aug '14

30 Aug '14

Thank you! I'm still lost in the forest of all lens functions and generality, and haven't expected this signature. Can someone recommend good reading on all the lens-related types and classes, what they represent and how can they be used? (interested not only in "how", but also "why") 30 авг. 2014 г. 11:20 пользователь "Benno Fünfstück" < benno.fuenfstueck(a)gmail.com> написал: > The lens operator that does this is %%~, also called `traverseOf`: > > λ: ("Hello", "World") & _1 %%~ (\a -> putStrLn a >> return a) > Hello > ("Hello","World") > > Also see the documentation: > http://hackage.haskell.org/package/lens-4.4.0.1/docs/Control-Lens-Traversal… > > -- > Benno > > > 2014-08-30 9:44 GMT+02:00 Nikolay Amiantov <nikoamia(a)gmail.com>: > >> Hello Cafe, >> >> I'm trying to wrap my head around 'lens' library. My current exercise is >> to modify something using Lens in monad. Say, >> >> ("Hello", "World") & _1 `myOp` (\a -> putStrLn a >> return a) >> >> in IO, where myOp would be of type: >> >> myOp :: Monad m => Lens s t a b -> (a -> m b) -> s -> m t >> >> Of course I can write it myself, using combination of "view" and "set": >> >> myOp lens f v = f (view lens v) >>= flip (set lens) v >> >> (have not checked this, but something like that should do), but is there >> a more elegant way? >> >> Nikolay. >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> >

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Using 'lens' for "over"-like computation in Monad
by Nikolay Amiantov 30 Aug '14

30 Aug '14

Hello Cafe, I'm trying to wrap my head around 'lens' library. My current exercise is to modify something using Lens in monad. Say, ("Hello", "World") & _1 `myOp` (\a -> putStrLn a >> return a) in IO, where myOp would be of type: myOp :: Monad m => Lens s t a b -> (a -> m b) -> s -> m t Of course I can write it myself, using combination of "view" and "set": myOp lens f v = f (view lens v) >>= flip (set lens) v (have not checked this, but something like that should do), but is there a more elegant way? Nikolay.

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