April 2017 - Haskell-Cafe

Downsides of the Prompt Monad
by Michael Litchard 07 Apr '17

07 Apr '17

Could someone outline for me the downsides of using the Prompt monad?

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[ANN] etc-0.0.0 Declarative configuration spec for Haskell projects
by Román González 07 Apr '17

07 Apr '17

Is my pleasure to announce a new library for managing configuration values on Haskell projects. Some features: * Have a versioned spec of all values your application can accept * Provides an API for gathering values from multiple sources (files, overwrite files, cli arguments, environment variables) and then composing them into a single configuration map * Gives a sane precedence over sources of the configuration value sources * Provides inspection utilities to understand why the configuration is the way it is * Provides an API that abstracts away the source of configuration values and allows easy casting into record types your application or other libraries understand * Supports both configuration files in JSON or YAML (when cabal flags are used) * Dynamically generates CLI inputs from spec configuration file Any feedback, or comments feel free to create a ticket or send me a tweet over at @romanandreg Cheers. Roman Gonzalez.-

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Re: [Haskell-cafe] What is a safe Haskell data type to store and manipulate Money values
by Doug McIlroy 07 Apr '17

07 Apr '17

> REFERENCES TO LITERATURE PLEASE Another domain with pertinent literature is proportional representation in legislative bodies. Sorry, I have no particular references to offer. Doug

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Package maintainership takeover: quickcheck-instances
by Oleg Grenrus 07 Apr '17

07 Apr '17

The quickcheck-instances provides QuickCheck type-classes' instances for Haskell Platform packages. Unfortunately, author and current maintainer Antoine Latter is quite unresponsive. There is handful of PR open [2], and I had to use Hackage Trustee powers to allow new versions of dependencies (to keep e.g. Stackage nightly going on). I have tried to contact him to offer a co-maintainership help (at 14.12.2016). Cheers, Oleg Grenrus - [1]: http://hackage.haskell.org/package/quickcheck-instances - [2]: https://github.com/aslatter/qc-instances/pulls

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What is a safe Haskell data type to store and manipulate Money values?
by Sandeep Cr 06 Apr '17

06 Apr '17

Hello all, What is a good data type for storing and manipulating monetary values in a typical web application with payment processing? What are the pros and cons of various options like Data.Scientific, Rational and Decimal?

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Re: [Haskell-cafe] [Haskell] Haskell Tools
by amindfv＠gmail.com 06 Apr '17

06 Apr '17

Moving this conversation to haskell-cafe! > El 6 abr 2017, a las 04:15, Boldizsár Németh <nboldi(a)caesar.elte.hu> escribió: > > Thanks for asking, I just added a note that you need to install the haskell-tools-daemon package to use the Atom plugin for Haskell Tools. > > If you want to run refactorings from a script or just without an editor, you can use haskell-tools-cli as well. > >> On 2017.04.06. 10:40, Ivan Lazar Miljenovic wrote: >> Is there support for anything except Atom at this time? >> >> I'm also unsure of what I need to install on my local machine if I >> want to try it out (do I need the daemon? or is the cli tool >> sufficient?). >> >>> On 6 April 2017 at 17:03, Boldizsár Németh <nboldi(a)caesar.elte.hu> wrote: >>> Dear Haskellers, >>> >>> I'm happy to announce a new tool for refactoring Haskell source code. >>> Check it out: http://haskelltools.org/ >>> >>> Best Regards, >>> Boldizsár Németh >>> _______________________________________________ >>> Haskell mailing list >>> Haskell(a)haskell.org >>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell

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Re: [Haskell-cafe] [ANN] etc-0.0.0 Declarative configuration spec for Haskell projects
by Geraldus 06 Apr '17

06 Apr '17

Román González: > Was too excited delivering the newspaper that I forgot to add it to the > email: > > Github repo: https://github.com/roman/Haskell-etc >

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2nd call for papers: Trends in Functional Programming, 19-21 june 2017, University of Kent, Canterbury
by Peter Achten 05 Apr '17

05 Apr '17

----------------------------- C A L L F O R P A P E R S ----------------------------- ======== TFP 2017 =========== 18th Symposium on Trends in Functional Programming 19-21 June, 2017 University of Kent, Canterbury https://www.cs.kent.ac.uk/events/tfp17/index.html The symposium on Trends in Functional Programming (TFP) 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, and other contributions (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. TFP 2017 will be the main event of a pair of functional programming events. TFP 2017 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on 22 June. The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * Soesterberg (The Netherlands) in 2014; * Inria Sophia-Antipolis (France) in 2015; * and Maryland (USA) in 2016. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == SCOPE == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: leading-edge, previously unpublished research work Position Articles: on what new trends should or should not be Project Articles: descriptions of recently started new projects Evaluation Articles: what lessons can be drawn from a finished project Overview Articles: summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2017 program chairs, Scott Owens and Meng Wang. == BEST PAPER AWARDS == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which ALL authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp17 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == INVITED SPEAKERS == Conor McBride University of Strathclyde (UK) Cătălin Hriţcu INRIA Paris (FR) == IMPORTANT DATES == Submission of draft papers: 5 May, 2017 Notification: 12 May, 2017 Registration: 11 June, 2017 TFP Symposium: 19-21 June, 2017 Student papers feedback: 29 June, 2017 Submission for formal review: 2 August, 2017 Notification of acceptance: 3 November, 2017 Camera ready paper: 2 December, 2017 == PROGRAM COMMITTEE == Co-Chairs Meng Wang University of Kent (UK) Scott Owens University of Kent (UK) PC Jeremy Yallop University of Cambridge (UK) Nicolas Wu University of Bristol (UK) Laura Castro University of A Coruña (ES) Gabriel Scherer Northeastern University (US) Edwin Brady University of St Andrews (UK) Janis Voigtländer Radboud University Nijmegen (NL) Peter Achten Radboud University Nijmegen (NL) Tom Schrijvers KU Leuven (BE) Matthew Fluet Rochester Institute of Technology (US) Mauro Jaskelioff CIFASIS/Universidad Nacional de Rosario (AG) Patricia Johann Appalachian State University (US) Bruno Oliveira The University of Hong Kong (HK) Rita Loogen Philipps-Universität Marburg (GE) David Van Horn University of Marylan (US) Soichiro Hidaka Hosei University (JP) Michał Pałka Chalmers University of Technology (SE) Sandrine Blazy University of Rennes 1 - IRISA (FR)

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Re: [Haskell-cafe] What is a safe Haskell data type to store and manipulate Money values?
by David Turner 04 Apr '17

04 Apr '17

On 4 Apr 2017 13:57, "David Turner" <dct25-561bs(a)mythic-beasts.com> wrote: > It's the currency conversions that will provide the most interesting > challenges in that list. If you were only working in a single currency then > something based on `Integer` would, I think, be fine. Perhaps `Int` or > `Int64` if you needed the extra speed. > > There are a number of different ways to implement multiple currencies > depending on your desired semantics and applicable accounting rules and > regulations. Peter Selinger has a good tutorial covering this at > http://www.mathstat.dal.ca/~selinger/accounting/tutorial.html > > One thing to watch out for: do you want to be able to do arithmetic on > amounts from different currencies? As in, do you want £5 + $5 to have a > meaningful result? If you can avoid this, life will be much simpler. > > > > On 4 Apr 2017 12:22, "Saurabh Nanda" <saurabhnanda(a)gmail.com> wrote: > >> Hi Manuel, >> >> Thank you for your reply. Some clarifications below... >> >> >>> It depends on what sort of computation you'll be doing upon those >>> monetary values and on the expectations of your users. It's typical >>> that payment processing applications sacrifice precision and instead >>> prefer to deal in exact quantities >> >> >> Is there a document which explains common use-cases for monetary values >> and best-practices for dealing with them? Any guidelines for which >> **Haskell** data-types to use for what kind of monetary calculations? >> >> Here is what we are doing in our app: >> >> * Powering web-based e-commerce checkout flows >> * Allowing store owners to input tax rates >> * Allowing end-customers to see product prices in different currencies >> (so, currency conversion) >> * Various reports to see total sales, total receivables, and total >> payables (basically a **very** small subset of small-business accounting) >> * Exporting data to full-fledged accounting systems, like Quickbooks and >> Xero. >> >> Based on this use-case, which Haskell data-type would you suggest? >> >> -- Saurabh. >> >> >> _______________________________________________ >> 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 ignores my config.yaml?
by Alexey Egorov 03 Apr '17

03 Apr '17

Hello haskellers, I'm trying to use stack scripting capabilities, but it gives me an error (and suggestion to fix it by adding some lines to extra-deps in config.yaml). However, adding this lines to config.yaml doesn't change anything. My script and config are here - https://pastebin.com/PyRMQtqw Any help would be appreciated.

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