- Haskell-Cafe - Haskell.org

Library for package preprocessing
by Carlo Nucera 06 Aug '15

06 Aug '15

Hi all, I'm writing a tool to analyze source code of a package, which uses haskell-src-extra. As copied from hackage, libraries may contain some extra stuff (for example, cpp directives). What is the modern way to preprocess the package (configuring for the environment, running the cpp ecc) to obtain code which is guaranteed to be parsed by haskell-src-extra? Ideally I'd like to leave most of the logic for this part outside of the package. Could you point me towards some libraries doing a similar thing? Best regards

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Where is Haskell Weekly News syndicated?
by Jeremy 06 Aug '15

06 Aug '15

Haskell Weekly News used to be syndicated on http://contemplatecode.blogspot.com/ and http://sequence.complete.org/hwn. sequence only has HWN up to March 2010, while contemplatecode goes up to the beginning of February. Is there any way that I can subscribe to HWN (preferably as RSS/Atom), and not other stuff that doesn't interest me? -- View this message in context: http://haskell.1045720.n5.nabble.com/Where-is-Haskell-Weekly-News-syndicate… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Voleon Capital Management Hiring Senior Software Engineer
by Charles Weitzer 05 Aug '15

05 Aug '15

Voleon Capital Management LP is a startup quantitative hedge fund located in Berkeley, California. We would like to hire a senior software engineer as soon as possible. Voleon's founders previously worked together at one of the most successful quantitative hedge funds in the world. Our CEO has a PhD in Computer Science from Stanford and has been CEO and founder of a successful Internet infrastructure startup. Our Chief Investment Officer has a PhD in Statistics from Berkeley. Voleon's team includes PhD's from leading departments in statistics, computer science, and mathematics. We have made several unpublished advances in the field of machine learning and in other areas as well. Here is our formal job description: ********************************************************** * Senior Software Engineer * Technology-driven investment firm employing cutting-edge statistical machine learning techniques seeks an exceptionally capable software engineer. You will architect and implement new production trading systems, machine learning infrastructure, data integration pipelines, and large-scale storage systems. The firm researches and deploys systematic trading strategies designed to generate attractive returns without being dependent on the performance of the overall market. Join a team of under 30 people that includes a Berkeley statistics professor as well as over ten PhD's from Berkeley, Chicago, CMU, Princeton, Stanford, and UCLA, led by the founder and CEO of a successful Internet infrastructure technology firm. The firm's offices are walking distance from BART and the UC Berkeley campus in downtown Berkeley, California. We have a casual and collegial office environment, weekly catered lunches, and competitive benefits packages. We seek candidates with a proven track record of writing correct, well-designed software, solving hard problems, and delivering complex projects on time. You should preferably have experience designing and implementing fault-tolerant distributed systems. Experience with building large-scale data infrastructure, stream processing systems, or latency-sensitive programs is a bonus. We are growing rapidly. Willingness to take initiative and a gritty determination to productize are essential. Required experience: - developing with C/C++/Python/Go in a Linux environment with a focus on performance, concurrency, and correctness. - experience with a functional programming language (Haskell, OCaml, Erlang) - working in TCP/IP networking, multi-threading, and server development. - working with common Internet protocols (IP, TCP/UDP, SSL/TLS, HTTP, SNMP, etc.). - architecting and designing highly available systems. - architecting and designing large-scale data management infrastructure. - working in large codebases and building modular, manageable code. Preferred experience: - debugging and performance profiling, including the use of tools such as strace, valgrind, gdb, tcpdump, etc. - working with build and test automation tools. - working with well-defined change management processes. - diagnosing RDBMS performance problems, exploiting indexing, using EXPLAIN PLAN, optimizing at the code layer, etc. - working with messaging queues (RabbitMQ, Redis, etc.) as well as distributed caching systems. Interest in financial applications is essential, but experience in finance is not a primary factor in our hiring. Benefits and compensation are highly competitive. ********************************************************** The above job description is just a starting point in terms of possible duties and seniority. We can be very flexible for the right person. If you are interested or if you know of anyone who might be interested, let me know the best way to get in touch and we can discuss details. Thank you, Charles Weitzer Senior Recruiter Voleon Capital Management LP Charles(a)Voleon.com<mailto:Charles@Voleon.com> Office: 510.704.9870 x 7012 Mobile: (510) 558-9182 www.Voleon.com

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Re: [Haskell-cafe] [Haskell-beginners] How would I increment or otherwise change a value in a record with “Simon-ness”
by Sumit Sahrawat, Maths & Computing, IIT (BHU) 05 Aug '15

05 Aug '15

More suitable for the haskell-cafe. Routing. On 6 August 2015 at 02:52, Michael Litchard <michael(a)schmong.org> wrote: > > The below code is from this tutorial http://dev.stephendiehl.com/hask/ > > it illustrates very well how to operate on values from records with > "Simon-ness" (illustrated below). What I am struggling with is how to > modify values inside records with "Simon-ness", say incrementing "age". I > keep thinking it has to do with the way Label is defined with the > constructor Get. Could I add another constructor Put? > > {-# LANGUAGE DataKinds #-}{-# LANGUAGE KindSignatures #-}{-# LANGUAGE MultiParamTypeClasses #-}{-# LANGUAGE FunctionalDependencies #-}{-# LANGUAGE FlexibleInstances #-}{-# LANGUAGE FlexibleContexts #-}{-# LANGUAGE StandaloneDeriving #-}{-# LANGUAGE ExistentialQuantification #-}{-# LANGUAGE ConstraintKinds #-} > > import GHC.TypeLits > newtype Field (n :: Symbol) v = Field { unField :: v } deriving Show > data Person1 = Person1 > { _age :: Field "age" Int > , _name :: Field "name" String > } > data Person2 = Person2 > { _age' :: Field "age" Int > , _name' :: Field "name" String > , _lib' :: Field "lib" String > } > deriving instance Show Person1deriving instance Show Person2 > data Label (l :: Symbol) = Get > class Has a l b | a l -> b where > from :: a -> Label l -> b > instance Has Person1 "age" Int where > from (Person1 a _) _ = unField a > instance Has Person1 "name" String where > from (Person1 _ a) _ = unField a > instance Has Person2 "age" Int where > from (Person2 a _ _) _ = unField a > instance Has Person2 "name" String where > from (Person2 _ a _) _ = unField a > > age :: Has a "age" b => a -> b > age pnt = from pnt (Get :: Label "age") > > name :: Has a "name" b => a -> b > name pnt = from pnt (Get :: Label "name") > -- Parameterized constraint kind for "Simon-ness" of a record.type Simon a = (Has a "name" String, Has a "age" Int) > > spj :: Person1 > spj = Person1 (Field 56) (Field "Simon Peyton Jones") > > smarlow :: Person2 > smarlow = Person2 (Field 38) (Field "Simon Marlow") (Field "rts") > > > catNames :: (Simon a, Simon b) => a -> b -> String > catNames a b = name a ++ name b > > addAges :: (Simon a, Simon b) => a -> b -> Int > addAges a b = age a + age b > > > names :: String > names = name smarlow ++ "," ++ name spj-- "Simon Marlow,Simon Peyton Jones" > > ages :: Int > ages = age spj + age smarlow-- 94 > > > _______________________________________________ > Beginners mailing list > Beginners(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners > > -- Regards Sumit Sahrawat

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Fwd: Syntax extension - adding import support to let/where bindings
by Mike Meyer 05 Aug '15

05 Aug '15

Arg. Didn't send this to the list. ---------- Forwarded message --------- From: Mike Meyer <mwm(a)mired.org> Date: Wed, Aug 5, 2015 at 12:16 PM Subject: Re: [Haskell-cafe] Syntax extension - adding import support to let/where bindings To: Evan Laforge <qdunkan(a)gmail.com> On Wed, Aug 5, 2015 at 11:43 AM Evan Laforge <qdunkan(a)gmail.com> wrote: > And while "you don't have to use it" is > always brought up, it seems to me the more successful the feature is > the more likely you do have to use it. > "You don't have to use it" is a canard, and that argument needs to be killed whenever and wherever it arises. Sure, I don't have to use it. But the tools I use have to support it, so it'll make them bigger and slower, so I'm paying the price for "it" even if I don't use it. If I'm on a team, I probably have to either waste time arguing with other people to get them not to use it, or at least explain why I didn't use it. And that latter will come up every time I share code with other people, which we do want to encourage people to do. And that brings us to the real issue of why "You don't have to use it" is simply false. Reusing other people's code is a critical part of any software development environment. If they use, I have to understand it in order to understand their code. Even more than I have to in order to explain why I don't use it. So, no matter what I think of some feature, if it exists, the tools I use will almost certainly have to support it, and I'll have to understand the feature well enough to decipher code that uses it, and probably defend my decision not to use it. I don't see that this is in any way less of a burden on me than if I chose to use it.

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Re: [Haskell-cafe] Syntax extension - adding import support to let/where bindings
by Oliver Charles 05 Aug '15

05 Aug '15

On Wed, Aug 5, 2015 at 3:12 PM Moritz Kiefer <moritz.kiefer(a)gmail.com> wrote: > Am Mittwoch, 5. August 2015 14:59:54 UTC+2 schrieb Mike Ledger: >> >> This would be really handy to have. You could also have import "blocks", >> like >> >> import Foo in { >> ... >> } >> >> Where {...} is a new layout block, I guess. >> > Is *let* not exactly this block feature? > Indeed, in my post I use let bindings to achieve this: let import CSS in [ width (px 50) ] You could also add other local bindings to your scope: let import CSS sizeInPx = px 50 in [ width sizePx, height sizeInPx ] (Note that just like let the other bindings have access to the symbols that were imported) *ocharles*

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Re: [Haskell-cafe] ambiguous module name Network.URI
by Kees Bleijenberg 05 Aug '15

05 Aug '15

Thanks Christopher, -----Oorspronkelijk bericht----- Check out the Hackage page for network-uri: https://hackage.haskell.org/package/network-uri The parseURI function is in the version of network you are using already so there is no need to import modules from network-uri. ---------------------------------------- If I remove the import of Network-URI and leave the import Network.Http and use parseURI, ghc complains: not in scope parseURI. Do I have to change someting in the packages? Kees

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Why is the no tuple syntax for sum types
by Silvio Frischknecht 05 Aug '15

05 Aug '15

Protuct types have this nice tuple syntax (a,Char,Int),(a,'c',1). Why is there no syntax like this for Sum types (a|Char|Int),(||1). This would be very usefull for some more explicit error handling. I.E. You have a library that has errors. Error1, .. ErrorN. Currently there are only two ways of making a function that can throw Error3 and Error8. Use 'Dynamic' typed Exceptions or make a general Error type that is the sum of all Errors. In both cases it is not clear from the type of the function what Errors can occur. With sumTuples you could just return (Result|Error3|Error8). Also, I guess I'm just one of those people who occasionally confuse Left and Right :) Silvio Frischknecht

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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 7.10.2-a
by Mark Lentczner 04 Aug '15

04 Aug '15

As promised in the Haskell Platform 7.10.2 announcement, we have now release Haskell Platform 7.10.2-a. The only changes from 7.10.2 are: text-1.2.1.3 - to work around the issue with text literals in GHC 7.10.2 fgl-5.5.2.1 - this release changes no APIs, but fixes builds with older GHCs Available, as always, from: https://www.haskell.org/platform/ - Mark

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Typeclassable typeclass?
by Zemyla 04 Aug '15

04 Aug '15

I apologize if this has been discussed and dismissed before, but I figured with Typeable being made entirely automatic by GHC, this might have a shot at working. What if there were a typeclass called Typeclassable, whose definition would be: class (Typeable a) => Typeclassable a where typeClass :: (Typeable c) => proxy c -> proxy' a -> ((c a) => b) -> b -> b So, for a simple example, you might have: nubT :: (Typeclassable a, Eq a) => [a] -> [a] nubT ls = typeClass (Proxy :: Proxy Ord) ls (nubOrd ls) (nub ls) where nubOrd is a suitable implementation of nub that requires Ord a. Basically, my first thought for the implementation of Typeclassable is that it contains all the dictionaries for a in a hashtable, and searches through them with the typeRep of c. So: 1) Can this be implemented with GHC as it is now? 2) Could this be implemented at all with any reasonable amount of work? 3) Should this be implemented? Would the benefits outweigh the costs?

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