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Is there a relation between the operational monad and the free monad?

Haskell on Reddit - Sat, 07/05/2014 - 1:10pm

Some time ago I learned about the operational semantics for monads in a blog post by /u/apfelmus. It seemed like a nice way to build a monadic DSL.

More recently I saw lots of internet discussion about the Free Monad, which is also a pattern that can be used to create monadic DSLs.

Is there a deeper algebraic relationship between those two patterns?

submitted by calsaverini
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Categories: Incoming News

CFP: PRDC2014 Call for Fast Abstracts / Industry Track Papers / Posters

General haskell list - Sat, 07/05/2014 - 2:44am
PRDC2014 Call for Fast Abstracts / Industry Track Papers / Posters Singapore Nov.18-21,2014 --------------------------------- Call for Fast Abstracts --------------------------------- Fast Abstracts at PRDC are short oral presentations, either on new ideas or work in progress, or opinion pieces that can address any issue relevant to dependable systems and networks. Because they are brief and have a later deadline, Fast Abstracts enable their authors to: .Summarise work that is not yet complete .Put forward novel or challenging ideas .State positions on controversial issues .Suggest new approaches to the solution of open problems Thus, they provide an excellent opportunity to introduce new work, or present radical opinions, and receive early feedback from the community. Contributions are particularly solicited from industrial practitioners and academics that may not have been able to prepare full papers du
Categories: Incoming News

async simplify code

haskell-cafe - Sat, 07/05/2014 - 1:58am
Hi Cafe, Is there any way to simplify this async code to somehow merge the withAsync code into the STM code? Looking at the code for tstABorCD it is not easy to see that it is really just (A&&B)||(C&&D). Here is the code: Thanks for any pointers, Grant _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

How to state semantics in denotational design?

haskell-cafe - Sat, 07/05/2014 - 12:49am
Dear all, This may seem a strange question due to my unfamiliarity with formal semantics, but bear with me. I am trying to apply denotational design principles to my library music-score, and often find myself writing down semantics of data structures in pseudo-Haskell such as The actual implementation of the data structures may or may not be identical to the semantics. For example, it makes sense to implement Span as (Time^2) or (Time x Duration), as these types are isomorphic. My question is basically: 1) Is my approach (using pseudo-Haskell) a sound way to state denotational semantics? 2) How can I state semantics (in code and/or documentation), and be sure that my implementation follow the semantics? I understand that the correctness of the implementation w.r.t. to the semantics can be verified using manual proofs, which worries me as I want to be able to refactor the semantics and be make sure that the implementation is still correct without having to repeat all the proofs. Is there a "trick" to e
Categories: Offsite Discussion

Signal Processing Library

haskell-cafe - Fri, 07/04/2014 - 6:19pm
Hello: I'm working on my Master's Thesis, and I need a signal processing library that can compute FFTs and autocorrelation on discrete data. Doesn't anyone have experience with such a package in Haskell? I appreciate your time. Sincerely, Jeremy Wright _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

HART 2014 - deadline extended

General haskell list - Fri, 07/04/2014 - 3:11pm
We extended the deadline until 12th July. ========================================= CALL FOR PAPERS Second Workshop on Haskell And Rewriting Techniques (HART 2014) To be held on September 5, co-located with ICFP 2014, the Haskell Symposium, etc., in Gothenburg. Haskell is an advanced purely-functional programming language. Pure functional programming is programming with equations, often defined by pattern-matching. Rewriting is the science of replacing equals by equals and thus a very powerful method for dealing with equations, often constructor-based. There are strong connections between Haskell (or generally, pure functional) programming and rewriting. The purpose of the HART workshop is to foster those connections. In addition to an invited talk by Oleg Kiselyov, we plan a half day of discussions, in an informal setting, on how Haskell (and related languages) and rewriting techniques and theories can cross-fert
Categories: Incoming News

Type-level Nat to Integer

haskell-cafe - Thu, 07/03/2014 - 10:03pm
Hi all, I'm trying to change type-level Nat to Integer as following: {-# LANGUAGE DataKinds, KindSignatures, GADTs, PolyKinds #-} data Nat = Z | S Nat class NatToInt n where natToInt :: n -> Int instance NatToInt Z where natToInt _ = 0 instance NatToInt (S n) where natToInt = 1 + natToInt (undefined :: n) I understand why it fails (Z and S have not the right kind). How to specify that NatToInt is Nat-specific? Moreover, if you have any advanced explanations/links which could give me a deeper understanding on what going on, I'll take them. Thanks in advance for your help. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
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Final Call for Papers: OCL 2014 Submissions Due in OneWeek

General haskell list - Thu, 07/03/2014 - 4:15pm
(Apologies for duplicates) CALL FOR PAPERS 14th International Workshop on OCL and Textual Modeling Applications and Case Studies (OCL 2014) Co-located with ACM/IEEE 17th International Conference on Model Driven Engineering Languages and Systems (MODELS 2014) September 28-30 (tbc), 2014, VALENCIA, SPAIN Modeling started out with UML and its precursors as a graphical notation. Such visual representations enable direct intuitive capturing of reality, but some of their features are difficult to formalize and lack the level of precision required to create complete and unambiguous specifications. Limitations of the graphical notations encouraged the development of text-based modeling languages that either integrate with or replace graphical notations for modeling. Typical examples of such languages are OCL, textual MOF, Epsilon, and Alloy. Textual modeling languages have thei
Categories: Incoming News

Haskell Weekly News: Issue 298

General haskell list - Thu, 07/03/2014 - 6:59am
Welcome to issue 298 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from June 15 to 28, 2014 Quotes of the Week * Kinnison * imagines a radio station playing only things like 'Life tru a Lens', stuff by 'Dire States' or 'Monadonna' Top Reddit Stories * Today I published an introductory book on Haskell Data Analysis Domain:, Score: 99, Comments: 26 Original: [1] On Reddit: [2] * Backpack: An ML-like module system for Haskell Domain:, Score: 76, Comments: 44 Original: [3] On Reddit: [4] * Cgrep, a context-aware grep for source code. Domain:, Score: 67, Comments: 13 Original: [5] On Reddit: [6] * Teenage Haskell Domain:, Score: 63, Comments: 7 Original: [7]
Categories: Incoming News

New gtk2hs 0.12.4 release

gtk2hs - Wed, 11/21/2012 - 12:56pm

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!


Categories: Incoming News