July 2012 - Libraries

Proposal: containers: add indexing operations for Set
by Patrick Palka 10 Jul '12

10 Jul '12

I'd like to add the following indexing operations for Data.Set.Set, to complement the existing functions for Data.Map.Map: findIndex :: Ord a => a -> Set a -> Int lookupIndex :: Ord a => a -> Set a -> Maybe Int elemAt :: Int -> Set a -> a deleteAt :: Int -> Set a -> Set a A tentative patch can be found here https://github.com/haskell/containers/pull/13 Discussion period: 2 weeks

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Proposal: Make digitToInt and intToDigit work up to base 36
by Twan van Laarhoven 05 Jul '12

05 Jul '12

Hello List, I propose to change the functions digitToInt and intToDigit in Data.Char to digitToInt :: Char -> Int digitToInt c | isDigit c = ord c - ord '0' | c >= 'a' && c <= 'z' = ord c - ord 'a' + 10 | c >= 'A' && c <= 'Z' = ord c - ord 'A' + 10 | otherwise = error ("Char.digitToInt: not a digit " ++ show c) intToDigit :: Int -> Char intToDigit i | i >= 0 && i <= 9 = toEnum (fromEnum '0' + i) | i >= 10 && i <= 35 = toEnum (fromEnum 'a' + i - 10) | otherwise = error "Char.intToDigit: not a digit" (and equivalently for the Ghc specialized version in Data.Show) Right now the functions only work for c <= 'f' and i <= 15, i.e. only up to hexadecimal. But I can think of no reason why that should be the case. There is the problem of compatibility with the Haskell98/2010 report. But since this proposed change only reduces the number of cases that are errors, I think that is not a big concern. Discussion period: 2 weeks, deadline July 13. Twan

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STM.check should have type Bool -> STM ()
by Favonia 05 Jul '12

05 Jul '12

Hi all, Recently I am using amazing STM to program concurrent programs at ease. However I am puzzled by the type of STM.check. Currently it has the type "Bool -> STM a" and returns undefined when the input is True. I think it should have been "Bool -> STM ()" and returned () instead. I couldn't image a situation that we need such generality in the type. Even worse, someone needs to write "void $ check x" or something to suppress warnings. In the paper "Beautiful Concurrency" the check function actually has the type "Bool -> STM ()". Thus, my question is, is there any good reason to have the type "Bool -> STM a" and to return undefined? If not, I am proposing this implementation (which is identical to the one in the Beautiful Concurrency): check :: Bool -> STM () check b = if b then return () else retry Thank fryguybob on the IRC for discussing with me. There's only a SO question on this: http://stackoverflow.com/q/8364903. By the way, STM.check seems to be the only undocumented API in the stm package. :-P Thanks, Favonia

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Proposal: add Functor instance to Control.Exception.Handler
by Patrick Palka 03 Jul '12

03 Jul '12

A Functor instance for Handler could be useful: e.g. foo :: IO (Maybe a) handlers :: [Handler ()] foo `catches` map (Nothing <$) handlers Proposed instance definition: instance Functor Handler where fmap f (Handler h) = Handler (fmap f . h) Deadline: 2 weeks

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Re: Proposal: Control.Concurrent.Async
by Sjoerd Visscher 03 Jul '12

03 Jul '12

On Fri, 15 Jun 2012 09:07:54 0100, Simon Marlow <marlowsd(a)gmail.com> wrote: > I still need to ponder the Applicative version, I'm not familiar with > Control.Newtype. I would still like the Traversable abstraction I > mentioned in my last message. Control.Newtype is not important. I added it just to be able to write ala' Concurrently traverse getURL urls instead of runConcurrently $ traverse (Concurrently . getURL) urls But it is probably nicer to have doConcurrently :: Traversable t => (a -> IO b) -> t a -> IO (t b) then you could write doConcurrently getURL urls and your doConcurrently would just be "doConcurrently id". I updated the code at https://gist.github.com/2926572 greetings, Sjoerd

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FTGL
by Eyal Lotem 01 Jul '12

01 Jul '12

I made a bunch of fixes and changes to FTGL. I can't find a maintainer's address. My fixes are all the commits after the "Version 1.333 from hackage" commit, which just mirrors the most updated hackage version. https://github.com/Peaker/FTGL/commits/master The most important fix is the NULL ptr check on the results from the ftgl C side, which is how it reports errors... Assuming the maintainer cannot be contacted, how can I get a new/fixed version uploaded? I have upload rights to hackage, can I simply upload a new version myself? -- Eyal

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