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Lazy patterns

haskell-cafe - Wed, 06/10/2015 - 3:00pm
Good day, I am trying to understand the lazy patterns as explained at If I type in the example without putting a ~ round the pattern sure enough I do not get an answer as the text says. What I completely fail to understand is why there is no CPU usage, increasing memory usage, stack overflow or other runtime error before I use ^C to stop it. What is going on under the hood ? Jon
Categories: Offsite Discussion

Brent Yorgey: Ally Skills Tutorial at ICFP

Planet Haskell - Wed, 06/10/2015 - 2:47pm

I just signed up for the Ally Skills Tutorial at ICFP, and if you are (1) a man who (2) will be at ICFP in Vancouver, I encourage you to sign up, too! From the website:

The Ally Skills Tutorial teaches men simple, everyday ways to support women in their workplaces and communities. Participants learn techniques that work at the office, in classrooms, at conferences, and online. The skills we teach are relevant everywhere, including skills particularly relevant to open technology and culture communities. At the end of the tutorial, participants will feel more confident in speaking up to support women, be more aware of the challenges facing women in their workplaces and communities, and have closer relationships with the other participants.

This sounds super helpful—I suspect there is often a large gap between the extent to which I want to support women and the extent to which I actually know, practically, how to do so. The workshop will be taught by Valerie Aurora, Linux filesystem developer and Ada Initiative co-founder; I expect it will be high quality!

Categories: Offsite Blogs

Relevance of frequently recommended programming books

Haskell on Reddit - Wed, 06/10/2015 - 1:51pm

Hi all,

I very much like to read programming books and I often stumble upon recommendations for programming books.

A few books I frequently get recommendations on are Clean Code and Code Complete. But as a beginner/intermediate functional programmer I always wonder how much these book are relevant to me. I have a very long list of books I wish to read and I wanted to ask for your opinions about these books and their relevance.

I would also appreciate hearing about other books you found extremely helpful.


submitted by gilmi
[link] [8 comments]
Categories: Incoming News

Help, can't find an old post.

Haskell on Reddit - Wed, 06/10/2015 - 1:29pm

Hi all

I remember seeing a post on here (at least I think it was here) about Application architecture best practices or something along those lines. I can't remember too many details except that I liked how it looked and it mentioned something about making .Ext modules for extending functionality or standard modules or something.

I know it's not much to go on, and I apologise but I've been searching google for a couple of hours now and I just can't work out the right incantations. I'm hoping someone here might remember what I'm talking about (or have written it!).

submitted by nicheComicsProject
[link] [2 comments]
Categories: Incoming News

Haskell code generating utility

Haskell on Reddit - Wed, 06/10/2015 - 10:23am

While playing with Scotty and building microservices I've found out that I'm writing too much boilerplate. I have created a utility ( to automate this. Have a look, may be you'll find it useful too! It may create template projects and template files. Right now there is a Scotty/JSON/MySQL template project and an entity template.

submitted by dbushenko
[link] [12 comments]
Categories: Incoming News

Haskell developer role with Strats at StandardChartered London

haskell-cafe - Wed, 06/10/2015 - 9:52am
Hi all, I'm hiring (another) Haskell dev to join our team in London. Details here: _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

Well-Typed.Com: Summer School on Generic and Effectful Programming

Planet Haskell - Wed, 06/10/2015 - 6:36am

I’m one of the lecturers at

Summer School on Generic and Effectful Programming

St Anne’s College, Oxford, 6th to 10th July 2015

(Register here)

Datatype-generic programming was the topic of my PhD thesis many years ago, and it has continued to be a fascinating field of work and research for me since then.

At the upcoming summer school, I will give a three-lecture course on Applying Type-level and Generic Programming in Haskell. In this course, I will describe the state-of-the-art of datatype-generic programming in Haskell/GHC. This means we’ll look at the GHC extension that allows you to generically derive your own type classes, but also at the relatively recent generics-sop library. We will discuss the GHC type system features that make all of this possible, such as data kinds, kind polymorphism, GADTs, higher-rank types, constraint kinds and more, and we will look at a number of real-world applications of generic programming, taken, e.g., from the areas of web programming and databases.

But my course is only one of many. Ralf Hinze, the main organizer, has done an outstanding job and assembled a fantastic lineup of lecturers: I’m honoured to be teaching alongside Edwin Brady, Fritz Henglein, Conor McBride, Don Syme and Tarmo Uustalu. I am sure I will learn a lot from them and their lectures.

If you always wanted to learn more about generic and effectful programming, this is your chance! You can still register for the school! I’d be happy to see you there.

Categories: Offsite Blogs

cannot build 'vector' with profiling

glasgow-user - Wed, 06/10/2015 - 5:18am
Hi all, I cannot build 'vector' (or 'cmdargs') with profiling on. specifically when I run: $ cabal install --enable-executable-profiling --enable-library-profiling --ghc-options="-O2 -rtsopts -prof -auto-all -caf-all" vector I get the message: Perhaps you haven't installed the "p_dyn" libraries for package ‛integer-gmp’ Per some advice I tried to add the '--disable-shared' $ cabal install --disable-shared --enable-executable-profiling --enable-library-profiling --ghc-options="-O2 -rtsopts -prof -auto-all -caf-all" vector but then I get this: Loading package primitive-0.6 ... <command line>: can't load .so/.DLL for: libHSprimitive-0.6.dylib (dlopen(libHSprimitive-0.6.dylib, 9): image not found) Any idea whats going on or for any work arounds? Pretty stumped! Thanks in advance! Ranjit. _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users< at >
Categories: Offsite Discussion

Don Stewart (dons): Haskell dev role in Strats at Standard Chartered [London]

Planet Haskell - Wed, 06/10/2015 - 2:27am

The Strats team at Standard Chartered has an open position for a typed functional programming developer, based in London.

You will work on the trading floor, directly with traders, building software to automate their work and improve their efficiency. The role is highly development focused and you will use Haskell for almost all tasks: data analysis, market data publishing, database access, web services, desktop GUIs, large parallel tasks, quantitative models, solvers, everything. This is a fast paced role – code you write today will be deployed within hours to hundreds of users and has to work.

This is a permanent position in London as part of the Strats global team. Demonstrated experience in typed FP (Haskell, OCaml, F# etc) is required. We have around 2.5 million lines of Haskell, and our own Haskell compiler. In this context we look for skill and taste in typed functional programming to capture and abstract over complex, messy systems.

Experience writing typed APIs to external systems such as databases, web services, pub/sub platforms is very desirable. We like working code, so if you have Hackage or github libraries, we definitely want to see them. We also like StackOverflow answers, blog posts, academic papers, or other arenas where you can show broad FP ability. A PhD in computer science is a strong advantage.

The role requires physical presence on the trading floor in London. Remote work is not an option. Ideally you have some project and client management skills — you will talk to users, understand their problems and then implement and deliver what they really need. No financial background is required.

More info about our development process is in the 2012 PADL keynote, and a 2013 HaskellCast interview.

If this sounds exciting to you, please send your resume to me – donald.stewart <at>

Role posted 2015-06-10

Tagged: jobs
Categories: Offsite Blogs

MonadFail proposal (MFP): Moving fail out of Monad

libraries list - Tue, 06/09/2015 - 9:43pm
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello *, the subject says it all. After we successfully put `=>` into Monad, it is time to remove something in return: `fail`. Like with the AMP, I wrote up the proposal in Markdown format on Github, which you can find below as a URL, and in verbatim copy at the end of this email. It provides an overview over the intended outcome, which design decisions we had to take, and how our initial plan for the transition looks like. There are also some issues left open to discussion. Here's a short abstract: - - Move `fail` from `Monad` into a new class `MonadFail`. - - Code using failable patterns will receive a more restrictive `MonadFail` constraint. Code without this constraint will be safe to use for all Monads. - - Transition will take at least two GHC releases. GHC 7.12 will include the new class, and generate warnings asking users to make their failable patterns compliant. - - Stackage sh
Categories: Offsite Discussion

[ANN] Lentil - a frugal issue tracker

General haskell list - Tue, 06/09/2015 - 6:36pm
lentil - a frugal issue tracker If you litter your code with TODOs and FIXMEs, lentil [1] can help you make sense of that big mess into something nice and readable like: src/Lentil/File.hs 49 does upMan work windows? [feature:intermediate] src/Lentil/Parse.hs 26 eliminate lookahead? refactor parsing? [lint] [refactor] 54 add test for rotoscope [test] It supports tags, filtering, exporting and much more. Check the user manual [2] for more information. [1] [2]
Categories: Incoming News

[Spoiler] Project Euler #24: why Haskell is syntactically awesome

Haskell on Reddit - Tue, 06/09/2015 - 4:58pm

(and operationally awesome, too)

Problem 24 asks us what the millionth (lexicographically ordered) permutation of [0,1,2,3,4,5,6,7,8,9]. How do we get this?

import Data.List (sort $ permutations $ [0..9]) !! 999999


submitted by Spewface
[link] [25 comments]
Categories: Incoming News