October 2016 - Libraries

Re: space leak in base or mtl
by Edward Kmett 06 Oct '16

06 Oct '16

At the least transformers should probably provide the manual overrides for <* and *> for all of the monad transformer data types. That should fix these cases. -Edward On Thu, Oct 6, 2016 at 5:08 AM, Zoran Bosnjak <zoran.bosnjak(a)via.si> wrote: > Dear base and mtl maintainers, > I would like to report a memory leak problem (not sure which haskell > component) when using "forever" in combination with "readerT" or "stateT". > Simple test program to reproduce the problem: > --- > import Control.Concurrent > import Control.Monad > import Control.Monad.Trans > import Control.Monad.Trans.Reader > import Control.Monad.Trans.State > > main :: IO () > main = do > -- no leak when using loop1 instead of loop2 > --let loop1 = (liftIO $ threadDelay 1) >> loop1 > let loop2 = forever (liftIO $ threadDelay 1) > > _ <- runStateT (runReaderT loop2 'a') 'b' > return () > --- > > I have asked on haskell-cafe, but the analysis is above my haskell > knowledge: > https://mail.haskell.org/pipermail/haskell-cafe/2016-October/125176.html > https://mail.haskell.org/pipermail/haskell-cafe/2016-October/125177.html > https://mail.haskell.org/pipermail/haskell-cafe/2016-October/125178.html > > regards, > Zoran > >

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looking for haskell-llvm list maintainer Erik de Castro Lopo
by Henning Thielemann 03 Oct '16

03 Oct '16

A bit off-topic: I tried to send an e-mail to haskell-llvm(a)projects.haskell.org It was refused, although an e-mail to the list was accepted a month ago. I tried to reach the list maintainer at: haskell-llvm-owner(a)projects.haskell.org Erik de Castro Lopo <mle+hs(a)mega-nerd.com> Erik de Castro Lopo <erikd(a)mega-nerd.com> No success. Any idea how to contact Erik or what is broken at haskell-llvm(a)projects.haskell.org?

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Generalise type of deleteBy
by Matthew Pickering 02 Oct '16

02 Oct '16

The type of `deleteBy` in `Data.List` could easily be generalised in a useful way. ``` deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a] ``` to ``` deleteBy :: (a -> b -> Bool) -> a -> [b] -> [b] ``` There is this closed ticket but no reasons for not generalising. https://ghc.haskell.org/trac/ghc/ticket/3399 Discussion Period: 1 week. Matt

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Proposal: add Monoid1 and Semigroup1 classes
by David Feuer 01 Oct '16

01 Oct '16

I've been playing around with the idea of writing Haskell 2010 type classes for finite sequences and non-empty sequences, somewhat similar to Michael Snoyman's Sequence class in mono-traversable. These are naturally based on Monoid1 and Semigroup1, which I think belong in base. class Semigroup1 f where (<<>>) :: f a -> f a -> f a class Semigroup1 f => Monoid1 f where mempty1 :: f a Then I can write class (Monoid1 t, Traversable t) => Sequence t where singleton :: a -> t a -- and other less-critical methods class (Semigroup1 t, Traversable1 t) => NESequence where singleton1 :: a -> t a -- etc. I can, of course, just write my own, but I don't think I'm the only one using such.

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