[Haskell-cafe] Minh Thu, please add me to your LinkedIn network
LinkedIn Kyle Hanson requested to add you as a connection on LinkedIn: -- Minh Thu, I'd like to add you to my professional network on LinkedIn. - Kyle Accept invitation from Kyle Hanson http://www.linkedin.com/e/uc6lxc-hlw276p4-5e/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/blk/I943132921_20/3wOtCVFbmdxnSVFbm8JrnpKqlZJrmZzbmNJpjRQnOpBtn9QfmhBt71BoSd1p65Lr6lOfP0OnP4Oej8PcjcQekALpQcJlDxQrDwLc3wRcP4Qc3gTdz4LrCBxbOYWrSlI/eml-comm_invm-b-in_ac-inv28/?hs=falsetok=0b7qQjv89PWlU1 View profile of Kyle Hanson http://www.linkedin.com/e/uc6lxc-hlw276p4-5e/rso/60831967/_LLG/name/22724543_I943132921_20/?hs=falsetok=2TI3wCxd1PWlU1 -- You are receiving Invitation emails. This email was intended for Minh Thu Vo. Learn why this is included: http://www.linkedin.com/e/uc6lxc-hlw276p4-5e/plh/http%3A%2F%2Fhelp%2Elinkedin%2Ecom%2Fapp%2Fanswers%2Fdetail%2Fa_id%2F4788/-GXI/?hs=falsetok=0-VFub_99PWlU1 (c) 2012, LinkedIn Corporation. 2029 Stierlin Ct, Mountain View, CA 94043, USA. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type-level integers, type-level operators, and most specific overlapping instance
TP wrote: But I have still a question: is the behavior of GHC correct in the example of my initial post? See here: http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/type-class-extensions.html#instance-overlap When matching, GHC takes no account of the context of the instance declaration (context1 etc). GHC's default behaviour is that exactly one instance must match the constraint it is trying to resolve. My misunderstanding came from a confusion between a context and a constraint. The context is what is before the =, and the constraint is what is after, i.e. the main part of the instance declaration. This is the reason why my context using an inequality test on type-level integers was not taken into account: if I understand well there must be only one instance that matches the constraint, independently from the contexts, before GHC checks that the instance context is indeed respected. The OverlappingInstances option only helps to have only one matching instance (independently from the contexts): if several instances match, but there is a more specific one, GHC selects this one and then checks the corresponding instance context. Thanks, TP ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type-level integers, type-level operators, and most specific overlapping instance
On Sun, Sep 22, 2013 at 11:07 AM, TP paratribulati...@free.fr wrote: My misunderstanding came from a confusion between a context and a constraint. The context is what is before the =, and the constraint is what is after, i.e. the main part of the instance declaration. Hi TP, I think context and constraint mean the same thing. The haskell report uses the word context for http://www.haskell.org/onlinereport/decls.html for the whole list and constraint for one part of that list (Eq a). With the extension -XConstraintKinds both of those are called Constraint. In other words: instance Context = InstanceHead instance (Constraint, Constraint2) = InstanceHead Regards, Adam ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type-level integers, type-level operators, and most specific overlapping instance
adam vogt wrote: I think context and constraint mean the same thing. The haskell report uses the word context for http://www.haskell.org/onlinereport/decls.html for the whole list and constraint for one part of that list (Eq a). With the extension -XConstraintKinds both of those are called Constraint. In other words: instance Context = InstanceHead instance (Constraint, Constraint2) = InstanceHead This is indeed more in accordance with what I believe to be a context or a constraint. But, it seems that in this page http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/type-class-extensions.html#instance-overlap the vocabulary is different: instance context1 = C Int a where ... -- (A) instance context2 = C a Bool where ... -- (B) instance context3 = C Int [a] where ... -- (C) instance context4 = C Int [Int] where ... -- (D) The instances (A) and (B) match the constraint C Int Bool, but (C) and (D) do not. When matching, GHC takes no account of the context of the instance declaration (context1 etc). [...] The -XOverlappingInstances flag instructs GHC to allow more than one instance to match, provided there is a most specific one. For example, the constraint C Int [Int] matches instances (A), (C) and (D), but the last is more specific, and hence is chosen. If there is no most-specific match, the program is rejected. So, what do I miss? Isn't the vocabulary different here? And I do not understand what is written if I take your definition (which is indeed the definition in the Haskell report). Thanks in advance, TP ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Minh Thu, please add me to your LinkedIn network
What a surprise, I didn't know the real name of Haskell Cafe till date, BUT today I came to know it: it is Minh Thu V. linked in sucks ... Thanks and regards, -Damodar Kulkarni On Sun, Sep 22, 2013 at 2:53 PM, Kyle Hanson via LinkedIn mem...@linkedin.com wrote: [image: LinkedIn] http://www.linkedin.com/e/uc6lxc-hlw276p4-5e/hom/?hs=falsetok=1F1OVFpS1PWlU1 Hi Minh Thu, I'd like to connect with you on LinkedIn. Accepthttp://www.linkedin.com/e/uc6lxc-hlw276p4-5e/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/blk/I943132921_20/1Bt6BSrCBTpmUJt71BoSdxbm8JrnpKqlZJrmZzbmNJpjRQnOpBtn9QfmhBt71BoSd1p65Lr6lOfP0OnP4Oej8PcjcQekALpQcJlDxQrDwLc3wRcP4Qc3gTdz4LrCBxbOYWrSlI/eml-comm_invm-b-accept-newinvite/?hs=falsetok=3WsXkZaBdPWlU1 View Profilehttp://www.linkedin.com/e/uc6lxc-hlw276p4-5e/rso/60831967/_LLG/name/22724543_I943132921_20/eml-comm_invm-b-profile-newinvite/?hs=falsetok=041BVcm2lPWlU1 http://www.linkedin.com/e/uc6lxc-hlw276p4-5e/rso/60831967/_LLG/name/22724543_I943132921_20/eml-comm_invm-b-photo-newinvite/?hs=falsetok=0kvDW_y0FPWlU1 Kyle Hansonhttp://www.linkedin.com/e/uc6lxc-hlw276p4-5e/rso/60831967/_LLG/name/22724543_I943132921_20/eml-comm_invm-b-name-newinvite/?hs=falsetok=2JMZQUFRhPWlU1 Engineer at eShares, Inc. Greater Chicago Area You are receiving Invitation emails. Unsubscribehttps://www.linkedin.com/e/uc6lxc-hlw276p4-5e/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/uns/20008/22724543/anmdibt9ekfs9vo/haskell-cafe%40haskell%2Eorg/uc6lxc-hlw276p4-5e/eml-comm_invm-f-unsub-inv28/?hs=falsetok=2n8GqjQ2lPWlU1. This email was intended for Minh Thu Vo (Core/Server Lead Developer at OpenERP). Learn why we included thishttp://www.linkedin.com/e/uc6lxc-hlw276p4-5e/plh/http%3A%2F%2Flinkedin%2Ecusthelp%2Ecom%2Fapp%2Fanswers%2Fdetail%2Fa_id%2F4788/2t30/?hs=falsetok=3DK9rbdq9PWlU1. © 2013, LinkedIn Corporation. 2029 Stierlin Ct. Mountain View, CA 94043, USA ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Music update
Will there be a video of the live premier? On Fri, Sep 20, 2013 at 12:14 PM, Mark Lentczner mark.lentcz...@gmail.comwrote: Some might remember me asking about music packages a while back... An update: I ended up using Euterpea, which in turn uses both Codec.Midi and Sound.PortMidi. My working environment was to have my code loaded up in ghci, play MIDI into a software MIDI bus, and pipe that into MainStage 3 which ran the synths. The piece I was working on premiered last night at a concert in Wellington, NZ. The live recording will take a while, but you can hear a studio synth recording (from the above setup) here: https://soundcloud.com/mtnviewmark/plain-changes-2-all-synth-mix The code for the piece is all open source: https://github.com/mzero/PlainChanges2. In particular, there is a somewhat improved MIDI playerhttps://github.com/mzero/PlainChanges2/blob/master/src/Sound/MidiPlayer.hs in there. Enjoy! - Mark P.S.: Yes, and now that that's done with, I can get on with the next Haskell Platform release! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Cabal install build of scion-browser 0.2.18 fails when linking Persistent-sqlite1.21
Hi I'm a Haskell newbie. I just installed Haskell on Windows 7 x64 (Haskell Platform 2013.2.0.0 containing GHC 7.6.3), and have been using cabal-install to build/install from Hackage all the helper executables required and/or supported by EclipseFP, the Eclipse Haskell Plugin. All the helper exe's installed without any issues, except for one: scion-browser 0.2.18. All its dependencies seemed to build fine, and it built fine up until the near the end of the link phase when the link to Persistent-sqlite 1.2.1 failed. Here is the error message (path information elided): Loading package persistent-sqlite-1.2.1 ... ghc.exe: *Unknown PEi386 section name `.drectve'* (while processing:\persistent-sqlite-1.2.1\libHSpersistent-sqlite-1.2.1.a) ghc.exe: panic! (the 'impossible' happened) (GHC version 7.6.3 for i386-unknown-mingw32): loadArchive persistent-sqlite-1.2.1\libHSpersistent-sqlite-1.2.1.a: failed Failed to install scion-browser-0.2.18 I understand what the message is saying, but I don't know how to go about resolving it. I have of course cleaned and retried a few times. But I get the same error. Any and all suggestions on how to resolve or work around this issue so that I can provide EclipseFP with a usable scion-browser, would be greatly appreciated. Thanks ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mystery of an Eq instance
On 20/09/2013, at 11:47 PM, damodar kulkarni wrote: There is an Eq instance defined for these types! So I tried this: *Main sqrt (10.0) ==3.1622776601683795 True *Main sqrt (10.0) ==3.16227766016837956 True *Main sqrt (10.0) ==3.1622776601683795643 True *Main sqrt (10.0) ==3.16227766016837956435443343 True It seems strange. But *WHY*? There is nothing in the least strange about this! Did it occur to you to try 3.1622776601683795 == 3.16227766016837956435443343 (Hint: the answer does not begin with F.) Four times you asked if the square root of 10 was equal to a certain (identically valued but differently written) number, and each time you got the same answer. Had any of the answers been different, that would have been shocking. So my doubts are: 1. I wonder how the Eq instance is defined in case of floating point types in Haskell? At least for finite numbers, the answer is compatibly with C, Fortran, the IEEE standard, and every programming language on your machine that supports floating point arithmetic using IEEE doubles. 2. Can the Eq instance for floating point types be considered meaningful? If yes, how? Except for infinities and NaNs, yes. As exact numerical equality. When you get into infinities and NaNs, things get trickier, but that's not at issue here. It seems to me that you may for some reason be under the impression that the 3. values you displayed have different values. As mathematical real numbers, they do. But they all round to identically the same numerical value in your computer. In general, programmers are **advised** not to base conditional branching on tests for **equality** of two floating point values. At least not until they understand floating point arithmetic. 3. Is this particular behaviour GHC specific? (I am using GHC 6.12.1) No. If there are references on this please share. The IEEE floating point standard. The LIA-1 standard. The C99 and C11 standards. What every computer scientist should know about floating point arithmetic -- citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.22.6768 Most of the unpleasant surprises people have with Haskell floating point numbers are *floating point* surprises, not *Haskell* surprises. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] GSoC Result - Communicating with Mobile devices - Push Notifications
I am happy to announce the result of 3 months working on the GSoC project: Communicating with mobile devices. After reading many documentation, looking for a good abstraction, learning about mobile apps and networks connections, and really valuable recommendations from my mentor, (I really want to thank Michael Snoyman for his availability and kindness) I succeeded in developing 3 libraries to make it easy to send push notifications to mobile devices. They are available on Hackage: ** push-notify-0.1.0.0 : *This library offers a simple API for sending notifications through APNS, GCM and MPNS. [1]http://hackage.haskell.org/package/push-notify-0.1.0.0 ** push-notify-ccs-0.1.0.0 :* This library offers an API for sending/receiving notifications through CCS (XMPP - Google Cloud Messaging). [2] http://hackage.haskell.org/package/push-notify-ccs-0.1.0.0 ** push-notify-general-0.1.0.0 : *This library offers a general API for sending/receiving notifications, and handling the registration of devices on the server. It provides a general abstraction which can be used to communicate through different services as APNS, GCM, MPNS, hiding as much as possible, the differences between them. [3]http://hackage.haskell.org/package/push-notify-general Now, it is easy to send/receive information with mobile devices, so you can develop server applications which interact with them. So, to clarify this, as part of this project, I developed many test examples, including Android/WPhone and Yesod apps. I really want to thank FPComplete for giving me the possibility of hosting the Yesod app. The code is available on GitHub: [4]https://github.com/MarcosPividori/GSoC-Communicating-with-mobile-devices and they are running online on: [5] http://gsoc.marcospividori.com.ar/ , so can be downloaded and tested on mobile devices. (BackAndForth Messaging and Connect4 apps) ** BackAndForth Messaging:* In this example, I show how to use the push-general library to handle the registration/reception and sending of messages. From a Yesod app [5]http://gsoc.marcospividori.com.ar/, you can send notifications to devices registered and receive messages from them. It is avaliable for Android and WPhone on [6]http://gsoc.marcospividori.com.ar/apps . ** Connect 4:* I have been thinking of an app which lets me show how useful push notifications are. The advantage of this notifications is that you can receive information from server when it is available without needing to continually poll. So, I started to think about a multiplayers game. Every time a player does something, you let the rest know about the new movement. So, I ran into the board game: Connect 4. Both, authenticated web players and users of the android app, can play one against each other. For actualizing the website [5] http://gsoc.marcospividori.com.ar/ , I use long polling, while for the Android app, push notifications. The Android app is available on [6]http://gsoc.marcospividori.com.ar/apps . Every feedback is welcome! Thanks, Marcos [1] http://hackage.haskell.org/package/push-notify-0.1.0.0 [2] http://hackage.haskell.org/package/push-notify-ccs-0.1.0.0 [3] http://hackage.haskell.org/package/push-notify-general [4] https://github.com/MarcosPividori/GSoC-Communicating-with-mobile-devices [5] http://gsoc.marcospividori.com.ar [6] http://gsoc.marcospividori.com.ar/apps ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
