April 2014 - Haskell-Cafe

[TFP2014] First Call for Participation
by Peter Achten 01 Apr '14

01 Apr '14

--------------------------------- 1ST CALL FOR PARTICIPATION --------------------------------- ======== TFP 2014 =========== 15th Symposium on Trends in Functional Programming May 26-28, 2014 Utrecht University Soesterberg, The Netherlands http://www.cs.uu.nl/wiki/TFP2014/WebHome Registration is now open for the symposium on Trends in Functional Programming (TFP). It is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results. Submission for TFP is now closed, and the complete programme (29 presentations and two invited talks) for TFP can be perused here: http://www.cs.uu.nl/wiki/TFP2014/PresentationSchedule TFP 2014 will be the main event of a pair of functional programming events. The other is the International Workshop on Trends in Functional Programming in Education (TFPIE). TFPIE will take place on May 25th. Its website is located at http://www.cs.uwyo.edu/~jlc/tfpie14/ . The submission deadline for TFPIE is April 21, 2014. INVITED SPEAKERS TFP is pleased to announce talks by the following two invited speakers: John Hughes of Chalmers, Goteborg, Sweden, is well-known as author of Why Functional Programming Matters, and as one of the designers of QuickCheck (together with Koen Claessen); the paper on QuickCheck won the ICFP Most Influential Paper Award in 2010. Currently he divides his time between his professorship and Quviq, a company that performs property-based testing of software with a tool implemented in Erlang. Geoffrey Mainland received his PhD from Harvard University where he was advised by Greg Morrisett and Matt Welsh. After a two year postdoc with the Programming Principles and Tools group at Microsoft Research Cambridge, he is now an assistant professor at Drexel University. His research focuses on high-level programming language and runtime support for non-general purpose computation. IMPORTANT DATES Early registration: April 14, 2014 Late registration: May 15, 2014 TFPIE Workshop: May 25, 2014 TFP Symposium: May 26-28, 2014 Registrations can be made at the following URL: http://www.cs.uu.nl/wiki/TFP2014/Register This page will also point you to the web page of the venue where you can arrange for your stay. hoping to see you there. Jurriaan Hage (General Chair)

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Re: [Haskell-cafe] Haskell Weekly News
by Roman Cheplyaka 01 Apr '14

01 Apr '14

(This was submitted to glasgow-haskell-users, probably by mistake. Redirecting to cafe.) * harry <voldermort(a)hotmail.com> [2014-03-31 00:36:10-0700] > There hasn't been a HWN since mid-December. I've emailed the editor with no > response, and there doesn't seem to have been any (public) online activity > from him since. > > I hope he's OK, but either way, it seems that HWN needs a new editor. Any > volunteers? While we're at it, I suggest to potential editors to look up how HWN looked back when Brent Yorgey was the editor. IMO it was much more interesting to read than a mechanically compiled list of reddit and SO posts which HWN has become lately. That style is more time and effort consuming, though. (http://ro-che.info/ccc/06) Roman

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groupBy without Ord?
by martin 01 Apr '14

01 Apr '14

Hello all, when I groupBy a list in order to cluster elements which satisfy some sort of equality, I usually have to sort the list first, which requires Ord. However groupBy itself does not require Ord, but just Eq. How can I groupBy a List whose elements are only instances of Eq but not of Ord?

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Re: [Haskell-cafe] Groundhog - Given entity, how to retrieve autokey value?
by lykahb＠gmail.com 01 Apr '14

01 Apr '14

Hi Ross, The primary key if it is generated by a database is not part of the entity. However, you can store it in your entity if you supply it yourself. It is a good approach if your entity has a natural primary key (like username). Only default key can be auto-incremented. Here is more detailed description of how keys work in Groundhog https://www.fpcomplete.com/user/lykahb/groundhog#keys-and-references Also you may want to use project instead of select. For example, "project (AutoKeyField, MyConstructor) $ MyField ==. myValue" would return id and the entity. Thank you, Boris Lykah On Sunday, March 30, 2014 12:41:40 AM UTC-4, Ross Pokorny wrote: > > Hello, > > I am trying to build a RESTful web application using Groundhog for > persistence. In order to generate URLs for my entities (e.g. for the > Location HTTP header), I need a way, given that I have an entity, to obtain > its id (its AutoKey). From what I've gathered so far, in normal Groundhog > usage, the primary key is not part of the actual entity datatype. The only > place where I've seen it returned is from the 'insert' functions in > Database.Groundhog. I need the id in cases where I have retrieved an > already-existing entity using 'select', but I cannot find a way to obtain > it. > > I gather that this might not be possible with the current API, and that > instead, I may need to explicitly define a field on the entity type to > store the id instead of using the auto-generated field that Groundhog > normally provides. In that case, my question is how do I set up that field > to be an auto-incrementing key, and not simply a value with a unique > constraint. Also, would Groundhog recognize that field as the AutoKey, and > would it return it from 'insert' calls? > > Thanks, > > Ross Pokorny >

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Re: [Haskell-cafe] [ANN] network-transport-zeromq-0.1.
by Patrick Wheeler 01 Apr '14

01 Apr '14

> Our vision is that send/expect should work according to the default distributed-process semantics, but one ought to be allowed to vary the semantics of channel-based communication (as opposed to actor-based) according to what is relevant to the application. E.g. an application ought to be able to give up reliability for better latency/throughput on a channel-by-channel basis. That pretty exciting. I will have to put aside some time to tryout Cloud Haskell on top of your ZeroMQ layer. I would love to see a simple example of how this would work with different reliability settings in a ping-pong example. On Mon, Mar 31, 2014 at 1:34 PM, Edsko de Vries <edsko(a)well-typed.com>wrote: > Hi Mathieu, > > That sounds great! It's great to see that the redesign of Cloud Haskell > with a pluggable Network.Transport layer is in fact being used. Good stuff! > > Edsko > > -- > You received this message because you are subscribed to the Google Groups > "parallel-haskell" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to parallel-haskell+unsubscribe(a)googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- Patrick Wheeler Patrick.John.Wheeler(a)gmail.com Patrick.J.Wheeler(a)rice.edu Patrick.Wheeler(a)colorado.edu

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