December 2016 - Haskell-Cafe

Use of errorWithoutStackTrace in the Prelude
by Alexis King 07 Dec '16

07 Dec '16

Hello, I noticed that the partial functions in the Prelude use errorWithoutStackTrace instead of `error` to provide their error messages, which produces significantly worse error messages. I stumbled into this when a coworker of mine had trouble tracking down a use of `head` that was throwing an exception, but didn’t include any information about where it was in the source. What exactly is the rationale for this? Is it to avoid the performance penalty of passing around the implicit parameter? That seems relatively unlikely, since the performance hit seems trivial, but perhaps it’s to avoid breaking tests that depend on error messages? I think it would be nice for Prelude-provided functions to be informative by default, so the change seems worth it to me, but I’m wondering if there’s something I’ve overlooked. Also, if the answer really is “no, errorWithoutStackTrace is correct”, is the expectation that people will use -prof if they want stacks? This seems a bit frustrating to a newcomer who might not understand anything more complicated than running `stack test` and might not be able to figure out how to pass the right options (especially since options need to be passed both at compile-time and at runtime). Thanks, Alexis

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Re: [Haskell-cafe] stack setup errors when user name has accents
by Andre Fernandes 06 Dec '16

06 Dec '16

> > This was due to a bug in the yaml package, apologies. It's been patched, > and the next version of Stack will have the bugfix. I believe the next > version will be released in the next few days, but if you're able to build > from master, you can use that. > Thanks a lot for your answer, it's good to know that soon the new Stack version will solve it. > > Here's the original issue, which includes a link to a temporary workaround: > https://github.com/commercialhaskell/stack/issues/2491 > > I'll take a look at that. > On Mon, Dec 5, 2016 at 8:13 PM, Andre Fernandes <fernand...(a)gmail.com > <javascript:>> wrote: > >> I am new in Haskell, and I am trying to use stack in my "Windows 10" >> machine to study a little more. >> >> Stack installed nicely, but when I run "stack setup" at the command >> prompt I get the following error: >> >> *"Could not parse 'C:\Users\Andr├®\AppData\Roaming\stack\config.yaml':* >> *InvalidYaml (Just (YamlException "Yaml file not found: >> C:\\Users\\Andr\233\\AppData\\Roaming\\stack\\config.yaml"))* >> >> *See http://docs.haskellstack.org/en/stable/yaml_configuration/ >> <http://docs.haskellstack.org/en/stable/yaml_configuration/>."* >> >> My name is "André" with an accent, and that's the problem, it can not >> find config.yaml at my windows user directory. Is there a way to solve this >> problem, maybe force stack to look into another folder, or something else? >> >> My windows command prompt encoding is 850, I do not not know if this info >> could help. >> >> Thanks in advance for any answer, >> André. >> >> _______________________________________________ >> Haskell-Cafe mailing list >> To (un)subscribe, modify options or view archives go to: >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> Only members subscribed via the mailman list are allowed to post. >> > >

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stack setup errors when user name has accents
by Andre Fernandes 06 Dec '16

06 Dec '16

I am new in Haskell, and I am trying to use stack in my "Windows 10" machine to study a little more. Stack installed nicely, but when I run "stack setup" at the command prompt I get the following error: *"Could not parse 'C:\Users\Andr├®\AppData\Roaming\stack\config.yaml':* *InvalidYaml (Just (YamlException "Yaml file not found: C:\\Users\\Andr\233\\AppData\\Roaming\\stack\\config.yaml"))* *See http://docs.haskellstack.org/en/stable/yaml_configuration/."* My name is "André" with an accent, and that's the problem, it can not find config.yaml at my windows user directory. Is there a way to solve this problem, maybe force stack to look into another folder, or something else? My windows command prompt encoding is 850, I do not not know if this info could help. Thanks in advance for any answer, André.

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Following-up on the laziness thread on Reddit
by Saurabh Nanda 06 Dec '16

06 Dec '16

Thoughts on this particular comment - https://www.reddit.com/r/haskell/comments/5fyg9e/how_important_is_laziness_… - from core GHC hackers would be very interesting and enlightening. -- Saurabh.

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Call for Haskell.org Committee Nominations
by Gershom B 05 Dec '16

05 Dec '16

Dear Haskellers, It is time to put out a call for new nominations (typically but not necessarily self-nominations) to the haskell.org committee. We have four members of our committee due for retirement -- Adam Foltzer, Nicolas Wu, Andres Loeh, and Edward Kmett (who is stepping down early). As per our bylaws, three of the slots will be for regular three year terms, and one will be a short one year term to fill out the remainder of Edward's. To nominate yourself, please send an email to committee at haskell.org by December 2, 2016. The retiring members are eligible to re-nominate themselves. Please feel free to include any information about yourself that you think will help us to make a decision. The Haskell.org committee serves as a board of directors for Haskell.org, a 501(c)3 nonprofit which oversees technical and financial resources related to Haskell community infrastructure. Being a member of the committee does not necessarily require a significant amount of time, but committee members should aim to be responsive during discussions when the committee is called upon to make a decision. Strong leadership, communication, and judgement are very important characteristics for committee members. The role is about setting policy, providing direction/guidance for Haskell.org infrastructure, planning for the long term, and being fiscally responsible with the Haskell.org funds (and donations). As overseers for policy regarding the open source side of Haskell, committee members must also be able to set aside personal or business related bias and make decisions with the good of the open source Haskell community in mind. We seek a broad representation from different segments of the Haskell world -- including but not limited to those focused on education, those focused on industrial applications, those with background in organizing users-groups, and those focused directly on our technical infrastructure. More details about the committee's roles and responsibilities are on https://wiki.haskell.org/Haskell.org_committee If you have any questions about the process, please feel free to e-mail us at committee at haskell.org, or contact one of us individually. Best, Gershom Bazerman

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[course announcement] Haskell for Life
by Sergiu Ivanov 05 Dec '16

05 Dec '16

Dear Haskell Cafe, This year I have taught and will teach a short course introducing people to Haskell. I realised that such a course might interest the subscribers of this list, so here is the course page, with all course materials (CC-BY licence): http://lacl.fr/~sivanov/doku.php?id=en:haskell_for_life Any feedback is welcome. (I will teach the next instance of the course in the following two weeks in Chișinău, Republic of Moldova, so if you happen to be around, don't hesitate to come by and give me a wink IRL ;-) ) -- Sergiu

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Fearing Haskell
by Henk-Jan van Tuyl 03 Dec '16

03 Dec '16

L.S., IBM's Watson can analyze web pages, see https://alchemy-language-demo.mybluemix.net/ . If I feed it the URL https://wiki.haskell.org/Haskell , Watson states that this page is about a person called Haskell, with a fearful sentiment. With the URL https://en.wikipedia.org/wiki/Haskell_(programming_language) , there is both joy and sadness in Haskell. :-) Regards, Henk-Jan van Tuyl -- Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://folding.stanford.edu/ http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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monad-coroutine alternatives
by Alex 02 Dec '16

02 Dec '16

Hello, Are there any data structures isomorphic to Coroutine[0] available on Hackage? -- Alex [0] https://hackage.haskell.org/package/monad-coroutine-0.9.0.3/docs/Control-Mo…

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