# News aggregator

### Monoid instance for Either that mappends both sides

Does something like this exist somewhere already?

newtype EitherMonoids a b = EitherMonoids (Either a b) deriving (Show) instance (Monoid a, Monoid b) => Monoid (EitherMonoids a b) where mempty = EitherMonoids $ Right mempty (EitherMonoids (Left xs)) `mappend` (EitherMonoids (Left ys)) = EitherMonoids $ Left $ xs `mappend` ys (EitherMonoids (Right xs)) `mappend` (EitherMonoids (Right ys)) = EitherMonoids $ Right $ xs `mappend` ys x@(EitherMonoids (Left _)) `mappend` (EitherMonoids (Right _)) = x (EitherMonoids (Right _)) `mappend` x@(EitherMonoids (Left _)) = x submitted by singpolyma[link] [11 comments]

Categories: Incoming News

### Neil Mitchell - DevOps with Haskell

Categories: Incoming News

### CfP LPNMR 2015 Announcement: SUBMISSIONS NOW OPEN!

[apologies for any cross-posting]
*** SUBMISSIONS ARE NOW OPEN ***
Call for Papers
---------------------------------------------------------------------------
13th International Conference on
Logic Programming and Non-monotonic Reasoning
LPNMR 2015
http://lpnmr2015.mat.unical.it/
Lexington, KY, USA
September 27-30, 2015
(Collocated with the 4th Conference on Algorithmic Decision Theory 2015)
---------------------------------------------------------------------------
AIMS AND SCOPE
LPNMR 2015 is the thirteenth in the series of international meetings on
logic programming and non-monotonic reasoning. LPNMR is a forum for
exchanging ideas on declarative logic programming, non-monotonic reasoning,
and knowledge representation. The aim of the conference is to facilitate
interactions between researchers and practition

Categories: Incoming News

### [EPIT2015] Call for participation to a Spring School about the Coq proof assistant

*** Call for participation, please distribute. ***
EPIT'2015 (http://www.epit2015.website)
Spring School in Theoretical Computer Science
Mechanizing Proofs of Programs in Coq
May 25 to May 29, 2015, Frejus, France
* Presentation
The french spring school in theoretical computer science (EPIT) is a
recurrent school which was created 40 years ago by Maurice Nivat.
This year, the school is about the mechanization of proofs of programs
using the proof assistant Coq. As no prerequisite is needed, the
school targets any computer scientist that is curious about what a proof
assistant is and how it can be integrated in its daily research work.
* Program
The school will take place between May 24 and May 29 and it will be
divided into eight sessions. A session will consist in a (rather
short) lecture (given in english) followed by practical exercises on
computer. The five first sessions will be dedicated to a presentation
of the main concepts and techniques

Categories: Incoming News

### [haskell.org Google Summer of Code] Call for Mentors

We have had a rather large pool of potential students apply for this year's
Google Summer of Code, but, ultimately, Google won't let us ask for a slot
unless we have a potential mentor assigned in advance.
On top of that, one thing we try to do with each project is wherever
possible, assign both a primary and a backup mentor, so the available
mentoring pool is drawn a little thin. Many hands make for light work,
though: If you've mentored or thought about mentoring in years past, I'd
encourage you to sign up on google-melange for the Google Summer of Code at:
https://www.google-melange.com/gsoc/homepage/google/gsoc2015
and request a connection to haskell.org as a Mentor.
Once you've done this you can help us vote on proposals, and should
something seem appropriate to you, you can flag yourself as available as a
potential mentor or backup mentor for one (or more) of the projects.
We have a couple of weeks left to rate proposals and request slots, but
it'd be good to make as much progress as we can this w

Categories: Incoming News

### skip hpc during build

I'm deleting hpc after building ghc for a vm to save space. Is there an easy
way to skip building it in the first place?
--
View this message in context: http://haskell.1045720.n5.nabble.com/skip-hpc-during-build-tp5768327.html
Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.

Categories: Offsite Discussion

### runghc and GhcWithInterpreter

I've built GHC with GhcWithInterpreter = NO. runghc is built and installed,
but errors out with "not built for interactive use".
Is runghc supposed to work with such a build? If not, why is it built at
all?
--
View this message in context: http://haskell.1045720.n5.nabble.com/runghc-and-GhcWithInterpreter-tp5768326.html
Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.

Categories: Offsite Discussion

### Proposal for a generic showIntAtBase

Hi,
The current implementation of showIntAtBase in Numeric is limited to Chars
currently.
*showIntAtBase*
* :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS*
The 2 reasons for this constraint is:
a) We only accept functions of the form (Int -> Char)
b) An implicit concatenation using (:)
I'd like to propose a new function showIntAtBaseGeneric that removes the
(Int -> Char) function constraint and takes an additional function to
replace the implicit (:) operator.
*showIntAtBaseGeneric*
* :: (Integral a1, Num b, Show a1) =>*
* a1 -> (b -> a) -> (a -> s -> s) -> a1 -> s -> s*
Now showIntAtBase may be implemented as:
*showIntAtBase :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS*
*showIntAtBase base toChr n0 r0 = showIntAtBaseGeneric base toChr (:) n0 r0*
The API and behavior of showIntAtBase remains unchanged while allowing for
generic conversions not limited to Chars alone.
*Example: *
*λ> showIntAtBaseGeneric 26 id (:) 500 [] -- convert 500 to base26 and
provid

Categories: Offsite Discussion

### A Random Strawman

Hello All,
Having skimmed the literature, run some tests and benchmarks:
The current System.Random is broken: https://github.com/haskell/random/issues/25#issuecomment-87423142. Furthermore, this is recorded in at least two published papers: http://dl.acm.org/citation.cfm?id=2660195 and http://publications.lib.chalmers.se/records/fulltext/183348/local_183348.pdf.
The tf-random package does not have this breakage and is based on good theoretical foundations.
In my tests tf-random performs better than System.Random.
As a result of which, I am very much inclined to suggest we replace the code in System.Random with tf-random. Before doing any more work on this, I’d like to understand what the next steps should be.
How much review should be carried out? I have no reason to doubt the implementors have done a great job but should someone (who?) review the code more formally. If so what would the process / tools be?
Tests in packages / applications may now fail as the (pseudo) random numbers will be different w

Categories: Offsite Discussion

### immortal profiling

https://ghc.haskell.org/trac/ghc/ticket/10235#ticket
Would be really useful to be able to profile code without dying, especially
in the context of a long-lived server. Am I missing something that would
allow me to do this?
cheers
mark
_______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users< at >haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users

Categories: Offsite Discussion

### New gtk2hs 0.12.4 release

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!

~d

Categories: Incoming News