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How does one read complicated type signatures?

haskell-cafe - Fri, 01/24/2014 - 5:54am
Hello world, I’ve just started playing with the http-conduit package and started inspecting type signatures of some of the functions, and I stumbled upon many things that look like this *Main Network.HTTP.Conduit> :t withManager withManager :: (monad-control- IO m, transformers- m) => (Manager -> resourcet-0.4.10:Control.Monad.Trans.Resource.Internal.ResourceT m a) -> m a The question is … how am I supposed to read these? It seems that they wrap around (maybe) 80 characters, which makes them unreadable … and the package prefixes also don’t really help. I’d like to point out here that I’m really a noob without any practical experience in Haskell, I’ve just read a few books. So I don’t have a problem understanding the concepts, but more and more often I find myself struggling just to read the type signature correctly Thanks for any tips, Jakub_____________
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haskell-cafe - Fri, 01/24/2014 - 1:02am
I've held the domain for a few years. I am not going to renew it. If you'd like to take it over, please let me know immediately and I'll send you an unlock code so you can transfer it. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

ARRAY'14 Call for Papers

General haskell list - Thu, 01/23/2014 - 9:50pm
ARRAY 14: ACM SIGPLAN International Workshop on Libraries, Languages and Compilers for Array Programming Co-located with PLDI 2014, Edinburgh, UK. A full-day workshop on Friday June 13th, following the main conference. A new workshop on Libraries, Languages and Compilers for Array Programming will have its first instance with PLDI this year (on June 13 in Edinburgh). The workshop aims to bring together the various groups (including functional programmers) that work on array programming. Papers from readers of this mailing list would be very welcome. The deadline for submission of four to six-page research or tool papers is April 2nd 2014, with notification on April 18th. Note the SIGPLAN sponsorship and the fact that students can apply for SIGPLAN PAC funding. It will be a fun workshop! For more information see and think about submitting! Mary Sheeran (with Laurie Hendren (Chair), Alex Rubinsteyn and Jan Vitek) ____
Categories: Incoming News

xkcd - Haskell

Haskell on Reddit - Thu, 01/23/2014 - 9:01pm
Categories: Incoming News

Philip Wadler: Gagging Law---still a problem

Planet Haskell - Thu, 01/23/2014 - 7:39pm
I had the following e-mail from my MP, Ian Murray; reprinted with permission. Photo shows 38 Degrees lobbying Murray's office last December. He is 3'rd from right, I am 3'rd from left.
I'm backing amendments to the Lobbing Bill todayBut the truth is that this terrible bill should be binnedThank you for contacting me about the Lobbying Bill. While some of you have contacted me for the first time this week, I have been keeping the majority of you up to date throughout this process. We are nearing the end of the bill's progress now, as today we begin the 'ping-pong' of amendments between the Lords and the Commons.

I must praise the work of 38 Degrees and other organisations in campaigning so hard on this issue. More people have contacted me on this bill than any other since the election in 2010. I had the pleasure of meeting a small number of campaigners from 38 Degrees towards the end of last year (picture above). They handed me a petition of thousands of people from across the UK firmly against the bill.Standing up for the wrong peopleThe government have got themselves in to a real mess with this gagging bill. After being forced in to a panic pause on part two they then had to grant a series of concessions. While those concessions make a bad bill slightly better, they don’t go far enough and the gag on charities and campaigners remains firmly in place.

That is why it is so important that the Commons votes to keep the two amendments that the Lords defeated the government on – the exclusion of some staff costs from the slashed spending limit, and the inclusion of special advisors in the definition of those who can be lobbied. I will be voting to keep those amendments in the bill and I will urge my colleagues to do the same.

Only David Cameron could present a Lobbying Bill that doesn’t stop commercial lobbyists influencing government policy, but could stop charities and campaigners from campaigning about it. No wonder people think he stands up for the wrong people.

This has been a bad bill from word go, and the government should’ve just gone back to the drawing board.

I have been leading for the Labour Party on part three of this bill, and have been pushing to make it a better piece of legislation. Unfortunately the government haven't listened to the thousands of people pushing to scrap this bill.

Thank you once again for getting in touch.

Yours sincerely,

Ian Murray MP
Working Hard for South Edinburgh 

The next day, I had the following update from 38 Degrees.
Dear Philip,

Here's a quick update on how it went today, with MPs voting again on the gagging law.

I’m afraid it's bad news. Most Conservative and Liberal Democrat MPs chose to follow party orders. They reversed the main improvements made in the House of Lords.

This means they voted:
- to remove new rules limiting secret lobbying by big business
- to put back in key limits on what campaigners, charities, and voluntary groups can do to speak up on issues of the day [1]

It’s pretty depressing. But it’s not over. The House of Lords will now get another vote – probably next week. They have the option to refuse to back down, and force MPs to vote yet again.

The votes were quite close. A number of government MPs did rebel - thanks in no small part to all the petitions, leaflets, emails and events which 38 Degrees members like you made happen.

If 17 more Conservative or Lib Dem MPs had voted differently, we would have won. Maybe we can get some more to change their minds next time around?

Details of how each MP voted will be posted on the 38 Degrees website, as soon as they are published (probably tomorrow morning).

All of us will need to think quickly about what we do next to stand up for democracy and freedom of speech. Options could include:
- a fresh push to encourage the Lords to hold firm next week
- naming and shaming MPs who voted to make the gagging law worse again today and pushing them to change their minds
- looking at options for legal challenges to the gagging law’s provisions
- thinking through ways we can keep campaigning and speaking up on the issues that matter despite the gagging law

Today, there's lots to feel fed up about. Yet again we’ve seen MPs push through a law which the public have never voted for, and which has been heavily criticised by everyone from the United Nations to the Citizens Advice Bureau, the Women’s Institute to the Royal British Legion. [2]

But there are reasons to feel hopeful too. This campaign has brought together so many different organisations and so many people from all walks of life. [3] Together we're proving that whilst faith in politicians is at an all time low, passion for real democracy is alive and kicking.

If you have thoughts or suggestions on what we should do together next, or just want to share how you're feeling, you can join the conversation on the 38 Degrees Facebook page, here:<wbr></wbr>peoplepowerchange

Alternatively, please reply to this email leaving the subject line the same.

I'll look forward to reading your thoughts.

Hopefully we can all agree on one thing, though. This definitely isn’t the time to give up. The kind of issues that 38 Degrees members choose to campaign on – like protecting the NHS, preserving our countryside, improving democracy and challenging tax dodging – are way too important to leave to politicians.

An alarming number of politicians seem to want us to shut up. But, I’m very glad to say, we’re just not going to!

Thanks for everything you do,

38 Degrees Executive Director

PS: On the subject of MPs wanting to shut us up, here's the story of the MP who called the police when 38 Degrees members visited him to deliver a petition!

And here's an MP saying it's "stupid" to email your MP!<wbr></wbr>Policy_and_Politics/article/<wbr></wbr>1228234/tory-mp-brands-38-<wbr></wbr>degrees-campaign-stupid/

PPS: MPs let us down today, but it isn't quite over yet - so please do share your ideas for what we could do next. Either by replying here or by posting on the 38 DegreesFacebook page:<wbr></wbr>peoplepowerchange

[1] There were 3 big votes in the Commons today:
- On the vote to require Ministers’ special advisors to record their meetings with lobbyists 311 MPs voted to reject the change, and 258 voted to accept them.
- On the vote to reject Lords’ changes to how much staff costs count towards total spending limits, amendment 108: 310 MPs voted to reject the changes, and 278 MPs to accept them into the Bill
- On the vote to reject Lords’ changes to the scope of what activity counts towards constituency spending limits, amendments 26 and 27: 314 MPs voted to reject the changes, and 274 MPs to accept them

[2] The Guardian: Lobbying bill will tarnish Britain, says UN official:<wbr></wbr>politics/2014/jan/12/lobbying-<wbr></wbr>bill-tarnish-britain-un-<wbr></wbr>official
National Federation of Women’s Institutes: Briefing page on the Lobbying Bill:<wbr></wbr>centre/latest-press-releases-<wbr></wbr>and-statements/lobbying-bill
Citizens Advice Bureau: Lobbying Bill briefings:<wbr></wbr>uk/index/campaigns/latest_<wbr></wbr>parliamentary_briefings.htm
The Royal British Legion: Lobbying Bill: Why asking politicians to back our troops could be stopped under this sloppy law:<wbr></wbr>uk/news-events/news/<wbr></wbr>campaigning/lobbying-bill-why-<wbr></wbr>asking-politicians-to-back-<wbr></wbr>our-troops-could-be-stopped-<wbr></wbr>under-this-sloppy-law

[3] Over 130 NGOs, including 38 Degrees, and over 160,000 people signed a petition against the gagging law: http://civilsocietycommission.<wbr></wbr>info/petition/
Categories: Offsite Blogs

Sorting a Repa Array

haskell-cafe - Thu, 01/23/2014 - 6:24pm
Hi, I am trying to parallellise genetic algorithms using haskell, but I get stuck at the stage where I need to sort the array of chromosomes based on their fitness. Using Repa, I am neither able to find a nice library implementation to sort an array, nor can I figure out how to generate a new array modifying only a few entries. I am not at a stage where I need to optimise execution time. It is still at the stage of learning exercise, wrt both to genetic algorithms, haskell, and splittable pseudo-random number generators. Thus, I would be grateful for both naïve and clever suggestions :-) Except for the sorting stage, the problem seems to well suited for Repa, with a chain of operations which can be mapped on the array. I am also planning to explore accelerate later for GPU work, and Repa seems to be a better step on the way than most other alternatives. My arrays are 1-D boxed arrays BTW. The entries are tuples including an Unboxed Vector (and a Double on which the sort order is defined). Doing it as
Categories: Offsite Discussion

And the Academy Award goes to... a literate program

Lambda the Ultimate - Thu, 01/23/2014 - 4:52pm

Matt Pharr, Greg Humphreys, and Pat Hanrahan have recently been given an Academy Award for Technical Achievement, for the book Physically Based Rendering. This is the first time the award has been given to a book and (more relevant to LtU) the first time a literate program has won an Academy Award.

Categories: Offsite Discussion


General haskell list - Thu, 01/23/2014 - 2:07pm
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Haskell tutorials

Haskell on Reddit - Thu, 01/23/2014 - 8:59am

I am new to haskell and need to learn it for a cs class. It was a bit of a curve ball. My background is exclusively in java and c++ so the 2 d structure and how modules are built is all very confusing. Could any of you point me in the right direction for a good series of haskell tutorials? Even a solid book would be helpful!

submitted by rags5903
[link] [15 comments]
Categories: Incoming News