Re: [Haskell-cafe] Problem with prepose.lhs and ghc6.10.1

be usable. -Edward Kmett On Thu, Apr 2, 2009 at 11:59 AM, Henry Laxen nadine.and.he...@pobox.comwrote: Dear Group, I'm trying to read the paper: Functional Pearl: Implicit Configurations at http://www.cs.rutgers.edu/~ccshan/prepose/ and when running the code in prepose.lhs I get: ../haskell

Re: [Haskell-cafe] Hackage not updating package list

. -Edward Kmett On Sun, Apr 5, 2009 at 12:47 PM, Don Stewart d...@galois.com wrote: johan.tibell: Hi, I just uploaded network-2.2.1. It appears on Hackage [1] but a `cabal update` followed by `cabal install network-2.2.1` results in: Resolving dependencies... cabal: There is no available

Re: [Haskell-cafe] Re: Configuring cabal dependencies at install-time

, it would allow me to fix my 'expression problem'. Others could introduce dependencies on the easier to install library allowing me to shrink the library and I would be able to install in more environments. -Edward Kmett On Tue, Apr 7, 2009 at 9:20 AM, John Dorsey hask...@colquitt.org wrote: John

Re: [Haskell-cafe] advice on space efficient data structure with efficient snoc operation

all of the instances. -Edward Kmett On Tue, Apr 7, 2009 at 7:49 AM, Manlio Perillo manlio_peri...@libero.itwrote: Hi. I'm still working on my Netflix Prize project. For a function I wrote, I really need a data structure that is both space efficient (unboxed elements) and with an efficient

Re: [Haskell-cafe] Looking for the fastest Haskell primes algorithm

You might want to start with the Sieve of Atkin: http://en.wikipedia.org/wiki/Sieve_of_Atkin -Edward On Tue, Apr 14, 2009 at 8:40 AM, Niemeijer, R.A. r.a.niemei...@tue.nlwrote: Today I happened to need a large list of prime numbers. Obviously this is a well-known problem, so I figured there

Re: [Haskell-cafe] Instancing Typeable for monad transformers?

I would happily supply a patch to add the Typeable (and the few Data instances that can be made) to transformers. I had to make similar ones in my comonad-transformers package anyways. -Edward Kmett On Wed, Feb 2, 2011 at 1:02 AM, John Millikin jmilli...@gmail.com wrote: Is there any

Re: [Haskell-cafe] ANN: unordered-containers - a new, faster hashing-based containers library

On Sat, Feb 19, 2011 at 7:27 PM, Sterling Clover s.clo...@gmail.com wrote: On Sat, Feb 19, 2011 at 3:04 PM, Johan Tibell johan.tib...@gmail.com wrote: On Sat, Feb 19, 2011 at 11:58 AM, Louis Wasserman wasserman.lo...@gmail.com wrote: A couple thoughts: size takes O(n). That's just

Re: [Haskell-cafe] ANN: hmpfr-0.3.2 (requires integer-simple, supports mpfr 3.0.0)

that were blocked by this. -Edward Kmett 2011/3/3 Michal Konečný m...@konecny.aow.cz Dear all, I am pleased to announce hmpfr-0.3.2, a new version of Aleš Bizjak's bindings to the MPFR arbitrary precision floating point arithmetic library. The changes in this version are quite small

Re: [Haskell-cafe] ANN: hmpfr-0.3.2 (requires integer-simple, supports mpfr 3.0.0)

repository up to date? -Edward Kmett On Fri, Mar 4, 2011 at 3:27 PM, Daniel Peebles pumpkin...@gmail.com wrote: According to Duncan Coutts (whom I asked about this issue in #ghc), the solution here is to use the new foreign import prim machinery to talk to MPFR. This prevents GC from occurring during

Re: [Haskell-cafe] Custom monad using ST

On Wed, Mar 9, 2011 at 6:21 PM, Yves Parès limestr...@gmail.com wrote: Well, I want to hide the fact that I'm using ST, so if I can hide the existential type 's' it is better. In practice if you want to actually _use_ ST you'll find you'll need to let the world escape into your type.

Re: [Haskell-cafe] How large is the Haskell community ?

Clearly we need some sort of xbox live -like achievement system for these. Achievement Unlocked: Stumped Oleg! On Sat, Feb 12, 2011 at 6:57 PM, Jan Christiansen j...@informatik.uni-kiel.de wrote: On 12.02.2011, at 21:18, Aaron Gray wrote: I was wondering if anyone had an idea or estimate

Re: [Haskell-cafe] [Agda] Defining subtraction for naturals

On Thu, Mar 17, 2011 at 6:41 PM, wren ng thornton w...@freegeek.org wrote: On 3/17/11 5:12 PM, Conor McBride wrote: On 17 Mar 2011, at 18:35, wren ng thornton wrote: Another question on particulars. When dealing with natural numbers, we run into the problem of defining subtraction. There

[Haskell-cafe] [haskell-gsoc] Haskell.org Google Summer of Code 2011

! -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] How to use roots package?

If your function has nice derivatives, you may want to look at the Newton implementation in http://hackage.haskell.org/packages/archive/ad/0.44.4/doc/html/Numeric-AD-Newton.html#v:findZero http://hackage.haskell.org/packages/archive/ad/0.44.4/doc/html/Numeric-AD-Newton.html#v:findZeroor if you

Re: [Haskell-cafe] Uncertainty analysis library?

I have a package for interval arithmetic in hackage http://hackage.haskell.org/package/intervals-0.2.0 However it does not currently properly adjust the floating point rounding mode so containment isn't perfect. However, we are actively working on fixing up the Haskell MPFR bindings, which will

Re: [Haskell-cafe] Uncertainty analysis library?

On Sun, Mar 20, 2011 at 5:46 PM, Tom Nielsen taniel...@gmail.com wrote: Interval arithmetic is of course not the same as uncertainty, although computer scientists like to pretend that is the case. (and uncertainty estimates do not have the be rough.) Very true. In general the propagation

Re: [Haskell-cafe] Uncertainty analysis library?

comment. I've pushed a new version of intervals to mollify hackage. It (or the old version) should cabal install just fine. -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] ANNOUNCE: incremental-parser library package

2011/3/22 Mario Blažević mblaze...@stilo.com This seems very interesting. One question: The MonadPlus and the Alternative instance differ: the former's mplus combinator equals the asymmetric | choice. Why? Good question. Basically, I see MonadPlus as a union of Monad and

Re: [Haskell-cafe] Looking for feedback on my attempt at a tree construction edsl

If you add an instance of IsString to handle leaf construction you can get it down to Fruits + do Apple Mango Arbitrary + do 1 ... But I also don't see the point of doing this in a monad. -Edward On Tue, Mar 22, 2011 at 1:15 PM, Yves Parès

Re: [Haskell-cafe] Uncertainty analysis library?

21, 2011 at 4:57 PM, Edward Kmett ekm...@gmail.com wrote: On Mon, Mar 21, 2011 at 2:42 PM, Edward Amsden eca7...@cs.rit.eduwrote: So I'm feeling a bit elated that I've sparked my first theoretical discussion in cafe, though I don't have much to contribute. :\ However in the interests

Re: [Haskell-cafe] SoC / Cabal project proposal: specify Setup.hs dependencies

On Tue, Mar 29, 2011 at 1:26 PM, Rogan Creswick cresw...@gmail.com wrote: I've been wanting to share code between cabal projects for some time, and I finally had a chance to write up the rough idea as a simple proposal. Here's the description, with links to the SoC trac and reddit

Re: [Haskell-cafe] Please add instance Semigroup Text

On Tue, May 3, 2011 at 12:04 PM, Bryan O'Sullivan b...@serpentine.comwrote: On Tue, May 3, 2011 at 8:00 AM, Yitzchak Gale g...@sefer.org wrote: Could you please add a Semigroup instance for Text? I'd strongly recommend writing an instance for the text package's Builder type instead.

Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

On Tue, May 3, 2011 at 7:12 AM, Yitzchak Gale g...@sefer.org wrote: Hi Edward, Thanks much for the very useful semigroups package. When using it in practice, it would be very useful to have an analogue to the mconcat method of Monoid. It has the obvious default implementation, but allows

Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

On Tue, May 3, 2011 at 3:43 PM, Yitzchak Gale g...@sefer.org wrote: Edward Kmett wrote: sconcat :: [a] - a - a with either the semantics you supplied or something like sconcat = appEndo . mconcat . map diff The sconcat we have been discussing is sconcat = flip $ appEndo . getDual

Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

:49 PM, Edward Kmett ekm...@gmail.com wrote: On Tue, May 3, 2011 at 3:43 PM, Yitzchak Gale g...@sefer.org wrote: Edward Kmett wrote: sconcat :: [a] - a - a with either the semantics you supplied or something like sconcat = appEndo . mconcat . map diff The sconcat we have been

Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

On Wed, May 4, 2011 at 7:40 AM, John Lato jwl...@gmail.com wrote: From: Edward Kmett ekm...@gmail.com On Tue, May 3, 2011 at 3:43 PM, Yitzchak Gale g...@sefer.org wrote: I'm sure there are countless other natural examples of semigroups in the wild, and that the typical non-trivial ones

Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

interconvert to [a]. -Edward On Tue, May 3, 2011 at 6:49 PM, Edward Kmett ekm...@gmail.com wrote: On Tue, May 3, 2011 at 3:43 PM, Yitzchak Gale g...@sefer.org wrote: Edward Kmett wrote: sconcat :: [a] - a - a with either the semantics you supplied or something like sconcat = appEndo . mconcat

Re: [Haskell-cafe] Data Flow Programming in FP

and Vene is packaged in 'streams' as Data.Stream.Future: http://hackage.haskell.org/packages/archive/streams/0.8.0/doc/html/Data-Stream-Future.html -Edward Kmett On Mon, Jun 20, 2011 at 10:45 AM, Richard Senington sc06...@leeds.ac.ukwrote: Hi all, I have recently become interested in Dataflow

[Haskell-cafe] [Haskell-Cafe] Constructive Probability Theory and RandProc's σ-algebras

On Sun, Jul 3, 2011 at 11:05 AM, David Banas dba...@banasfamily.net wrote: v0.4 of `RandProc` has just been posted to Hackage: http://hackage.haskell.org/package/randproc [NB: I transfered this discussion from haskell to haskell-cafe, and started another thread] I have been spending some

Re: [Haskell-cafe] Proposal #3339: Add (+) as a synonym for mappend

I originally didn't have the package exporting those things. I would be amenable to standardization without them, but I use them in about 20 packages that are built on top of semigroups, and naturals and non-empty lists come up when talking about semigroups a lot. Rather than having them live

Re: [Haskell-cafe] regex-applicative library needs your help! (algorithmic challenge)

On Sep 18, 2011, at 11:28 AM, Brandon Allbery allber...@gmail.com wrote: On Sat, Sep 17, 2011 at 22:11, Anton Tayanovskyy anton.tayanovs...@gmail.com wrote: By the way, can Haskell have a type that admits regular expression and only those? I mostly do ML these days, so trying to write up a

Re: [Haskell-cafe] Where is SNMap for stable names?

I have a stable-maps package that provides lookup and inserting into a map via stable names. -Edward On Thu, Sep 22, 2011 at 5:47 AM, Sean Leather leat...@cs.uu.nl wrote: There is an abstract type called SNMap for stable names referred to in [1]. This has apparently disappeared from GHC a

Re: [Haskell-cafe] Where is SNMap for stable names?

Then don't do that. =) I should have mentioned, parametric keys are a no no and can do bad things. ;) -Edward On Thu, Sep 22, 2011 at 2:33 PM, James Cook mo...@deepbondi.net wrote: I may be wrong, but I think the original SNMap was a map from 'StableName's to the specific values they were

Re: [Haskell-cafe] Where is SNMap for stable names?

You still need IO to get the stable name out to use. :) Sent from my iPad On Sep 23, 2011, at 5:33 AM, Sean Leather leat...@cs.uu.nl wrote: Hi Edward, On Thu, Sep 22, 2011 at 16:50, Edward Kmett wrote: I have a stable-maps package that provides lookup and inserting into a map via stable

Re: [Haskell-cafe] Where is SNMap for stable names?

Import Data.HashTable import Data.Dynamic table :: HashTable StableName Dynamic table= new (==) hashStableName 2011/9/22 Edward Kmett ekm...@gmail.com I have a stable-maps package that provides lookup and inserting into a map via stable names. -Edward On Thu, Sep 22, 2011 at 5

Re: [Haskell-cafe] haskell i18n best practices

haven't bundled it up for third party use yet, but its *my* practice. ;) -Edward Kmett This is what I've been looking at lately. The first thing I noticed was the GNU gettext implementation for Haskell. The wiki page [1] has a nice explanation by Aufheben. The hgettext package is found here [2

[Haskell-cafe] ANNOUNCE: Hac Boston from January 21-23rd at MIT

://haskell.org/haskellwiki/Hac_Boston/Talks . We look forward to seeing you at MIT! -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] ANNOUNCE: Hac Boston from January *20-22* at MIT

Correction: January 20-22nd ;) On Tue, Oct 25, 2011 at 5:45 PM, Edward Kmett ekm...@gmail.com wrote: I am very pleased to officially announce Hac Boston, a Haskell hackathon to be held January 21-23, 2012 at MIT in Cambridge, MA. The hackathon will officially kick off at 2:30 Friday

Re: [Haskell-cafe] ANN: Haskell OpenGL package updates

Jason, Thank you for taking ownership of HOpenGL! I would like to make a formal request for there to be *some* way to get access to either Graphics.Rendering.OpenGL.Raw.Core31.TypesInternal or that Graphics.Rendering.OpenGL.Raw.Core31.Types re-export the newtype wrappers it places around

Re: [Haskell-cafe] ANN: Haskell OpenGL package updates

, 2011 at 2:07 PM, Edward Kmett ekm...@gmail.com wrote: Jason, Thank you for taking ownership of HOpenGL! Thanks! I would like to make a formal request for there to be some way to get access to either Graphics.Rendering.OpenGL.Raw.Core31.TypesInternal

[Haskell-cafe] We *have* been accepted into the Google Summer of Code

Just to clarify, since I've been getting a ton of emails on the topic, we *have* been accepted to the Google Summer of Code this year. The list on their site is still updating, and we should appear there shortly. -Edward ___ Haskell-Cafe mailing list

[Haskell-cafe] Google Summer of Code 2012

very much and we look forward to another successful Summer of Code! -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] Un-memoization

It depends on how you are building the tree. If you are building up the tree from repeated substitution at the leaves and never reference its body before you do the final fold, you may be able to exploit the fact that trees form a free monad, and that there is a nice construction for increasing

Re: [Haskell-cafe] Problem Installing ad (Automatic Differentiation) Package

I'll need to get an older ghc version installed, so I can try to figure out what changes are needed to make template haskell bits compatible back to the current platform. 'ad' uses TH rather extensively, and sadly, the update to support ghc 7.4.1 broke a fair bit of the old code gen -- as I

Re: [Haskell-cafe] Have you seen this functor/contrafunctor combo?

Here is a considerably longer worked example using the analogy to J, borrowing heavily from Wadler: As J, this doesn't really add any power, but perhaps when used with non-representable functors like Equivalence/Comparison you can do something more interesting. -- Used for Hilbert {-# LANGUAGE

Re: [Haskell-cafe] Have you seen this functor/contrafunctor combo?

As an aside, the Union constraint on epsilon/gepsilon is only needed for the :+: case, you can search products just fine with any old contravariant functor, as you'd expect given the existence of the Applicative. -Edward On Sat, Jun 9, 2012 at 6:28 PM, Edward Kmett ekm...@gmail.com wrote: Here

[Haskell-cafe] haddock changes between 2.10 and 2.12?

Was there some significant change/bug introduced to haddock made between 2.10 and 2.12? When I look at the haddocks for kan-extensions 3.1: Data.Functor.Yonedahttp://hackage.haskell.org/packages/archive/kan-extensions/3.1/doc/html/Data-Functor-Yoneda.html which purports to have been built by

Re: [Haskell-cafe] Safe lens?

Actually Control.Lens.Getter doesn't use TH. The issue is more that it depends on some modules I didn't flag as Trustworthy and which require some more high-falutin type system extensions that GHC isn't happy about treating as Safe. I'll try adding a few Trustworthy flags. It previously was

Re: [Haskell-cafe] Safe lens?

in the event of Trustworthy. Particularly fancy if integrated into the haddocks. -mgsloan On Mon, Oct 29, 2012 at 2:33 PM, Edward Kmett ekm...@gmail.com wrote: Actually Control.Lens.Getter doesn't use TH. The issue is more that it depends on some modules I didn't flag as Trustworthy and which

Re: [Haskell-cafe] Safe lens?

future accidental toggleage. Still, it's puzzling that the status of Safe-Infered was lost. On Mon, Oct 29, 2012 at 2:46 PM, Edward Kmett ekm...@gmail.com wrote: I fixed it. Version 3.0.6 was just uploaded to hackage and is appropriately Trustworthy where needed. Please let me know if I

Re: [Haskell-cafe] Need some advice around lazy IO

Konstantin, Please allow me to elaborate on Dan's point -- or at least the point that I believe that Dan is making. Using, let bug = Control.DeepSeq.rnf str `seq` fileContents2Bug str or ($!!) will create a value that *when forced* cause the rnf to occur. As you don't look at bug until much

[Haskell-cafe] [haskell.org Summer of Code 2013] We're In!

to pester me (or Shachaf) with questions! -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] Automated Differentiation of Matrices (hmatrix)

hmatrix and ad don't (currently) mix. The problem is that hmatrix uses a packed structure that can't hold any of the AD mode variants we have as an Element. =( I've been working with Alex Lang to explore in ad 4.0 ways that we can support monomorphic AD modes and still present largely the same

Re: [Haskell-cafe] Automated Differentiation of Matrices (hmatrix)

Apr 2013, at 23:03, Edward Kmett ekm...@gmail.com wrote: hmatrix and ad don't (currently) mix. The problem is that hmatrix uses a packed structure that can't hold any of the AD mode variants we have as an Element. =( I've been working with Alex Lang to explore in ad 4.0 ways that we can

Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?

That is because every other language conflates the notion of a class with a vtable smashed into every inhabitant of the class where everything has to be defined together in one monolithic definition. You also can't write sensible Monads in those languages (Where does return go?) or retroactively

Re: [Haskell-cafe] Backward compatibility

Tantamount to a new language to fix a minor detail in a typeclass hierarchy? That is just histrionic. *No* language is that stable. Scala makes dozens of changes like that between *minor* versions, and while I hardly hold up their development practices as the best in the industry it is still

Re: [Haskell-cafe] Backward compatibility

So basically it boiled down drop the haskell98 package dependency and use the new exception system, and import the right things to avoid the use of the no longer exported Prelude catch? On Fri, May 3, 2013 at 12:44 PM, Niklas Hambüchen m...@nh2.me wrote: While I certainly enjoy the discussion,

Re: [Haskell-cafe] Infrastructure for testing the impact of a Functor/Applicative/Monad hierarchy

There is a chicken and the egg problem with this argument. Historically Haskell' has only considered changes that have been actually implemented. I would encourage the language standard to follow suit, but we survived a similar autocratic minor change to Num with very little ecosystem

[Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

. Shachaf Ben-Kiki is helping out as this year's backup administrator and he should also be able to help out with administrivia or questions as well. I'd like to thank everyone for participating in the selection process and I think we can look forward to another excellent summer of code! Edward Kmett

Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

or if my answer didn't suffice please feel free to follow up! -Edward Kmett On Tue, May 28, 2013 at 6:52 AM, Dominic Steinitz domi...@steinitz.orgwrote: Hi Edward, Although the project I am interested in (as a user) has been accepted :-), I can't help feeling the selection process is a bit

Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

of such a proposal that we've had in recent years. -Edward On Tue, May 28, 2013 at 8:24 PM, Ben Lippmeier b...@ouroborus.net wrote: On 29/05/2013, at 1:11 AM, Edward Kmett wrote: This unfortunately means, that we can't really show the unaccepted proposals with information about how to avoid

Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

There should be a link from the google-melange website, but one slight shift in focus is on either getting SWIG bindings or possibly even using Ian-Woo Kim's C++FFI tools. Carter may be able to go into more detail. On Wed, May 29, 2013 at 6:46 AM, harry volderm...@hotmail.com wrote: Edward

Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

per se but it is good to keep such a concrete goal in mind when working on something as abstract as SWIG. I agree that Qt has a somewhat horrible API. =) -Edward On Wed, May 29, 2013 at 12:34 PM, harry volderm...@hotmail.com wrote: Edward Kmett ekmett at gmail.com writes: There should

Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects

but there may be a free equivalent Dominic Steinitz domi...@steinitz.org http://idontgetoutmuch.wordpress.com On 28 May 2013, at 16:11, Edward Kmett ekm...@gmail.com wrote: Hi Dominic, The proposal is admittedly rather unfortunately opaque. The parts I can shed light on: Students come

[Haskell-cafe] [haskell.org Google Summer of Code] The Summer of Code is officially under way.

The getting to know your mentor period has passed and the Summer of Code has officially begun. Keep in mind that mid-term evaluations will begin July 29th, so students will need to hit the ground running. I'm looking forward to seeing what we can accomplish together this year! -Edward

Re: [Haskell-cafe] Proposal: Non-recursive let

On Wed, Jul 10, 2013 at 3:47 AM, o...@okmij.org wrote: Jon Fairbairn wrote: It just changes forgetting to use different variable names because of recursion (which is currently uniform throughout the language) to forgetting to use non recursive let instead of let. Let me bring to the

Re: [Haskell-cafe] Proposal: Non-recursive let

, Carter Schonwald wrote: Yup. Nested cases *are* non recursive lets. (Can't believe I forgot about that ) On Thursday, July 11, 2013, Edward Kmett wrote: On Wed, Jul 10, 2013 at 3:47 AM, o...@okmij.org javascript:_e({}, 'cvml', 'o...@okmij.org'); wrote: Jon Fairbairn

Re: [Haskell-cafe] Proposal: Non-recursive let

This happened because I copied the surrounding style blindly. I fucked up. state f = get = \s - case f s of (a, s) - do put s return a would not have the problem and would have given a warning about name shadowing. I for one am somewhat neutral on the *adding* a non-recursive let

Re: [Haskell-cafe] Proposal: Non-recursive let

FWIW, I maintain, according to wc and sloccount, 220841 lines worth of Haskell code at present. I have been bitten this error one time, so it affects me .45% of the time and that was only because it was in the only package I was not using -Wall on. -Edward On Wed, Jul 17, 2013 at 12:23 PM,

Re: [Haskell-cafe] Proposal: Non-recursive let

let x = x +1 is perfectly cromulent when x is sufficiently lazy, e.g. in the one point compactification of the naturals: data Conat = S Conat | Z There it represents infinity with proper sharing. -Edward On Jul 22, 2013, at 10:24 AM, Andreas Abel andreas.a...@ifi.lmu.de wrote: On

Re: [Haskell-cafe] Proposal: Non-recursive let

is a lazy constructor. On 22.07.13 4:54 PM, Edward Kmett wrote: let x = x +1 is perfectly cromulent when x is sufficiently lazy, e.g. in the one point compactification of the naturals: data Conat = S Conat | Z There it represents infinity with proper sharing. -Edward On Jul 22, 2013

Re: [Haskell-cafe] Proposal: Non-recursive let

I'm just going to say that I'd rather we didn't resort to calling each others trolls. I happen to disagree with Oleg on this particular issue and find that it is better resolved by just using -Wall or a 2-line combinator, but I find that across the breadth and depth of issues in the Haskell

Re: [Haskell-cafe] Proposal: Non-recursive let

Or fmap in this case =) On Wed, Jul 31, 2013 at 11:33 AM, Erik Hesselink hessel...@gmail.comwrote: On Fri, Jul 26, 2013 at 6:44 PM, Andreas Abel andreas.a...@ifi.lmu.de wrote: mapSnd f = (id *** f) As a very small aside, this is just `second` from Control.Arrow. Erik

Re: [Haskell-cafe] Impredicative types and Lens?

You can't write that lens by hand, so it isn't surprising that the template haskell can't generate it either. =) ImpredicativeTypes don't work all that well. -Edward On Sun, Sep 8, 2013 at 9:49 AM, Artyom Kazak y...@artyom.me wrote: Here’s a small example, which, when compiled, gives an

Re: [Haskell-cafe] Proposal: Partitionable goes somewhere + containers instances

I don't know that it belongs in the standard libraries, but there could definitely be a package for something similar. ConstraintKinds are a pretty hefty extension to throw at it, and the signature written there prevents it from being used on ByteString, Text, etc. This can be implemented with

Re: [Haskell-cafe] Proposal: Partitionable goes somewhere + containers instances

On Sun, Sep 29, 2013 at 8:20 AM, Edward Kmett ekm...@gmail.com wrote: I don't know that it belongs in the standard libraries, but there could definitely be a package for something similar. ConstraintKinds are a pretty hefty extension to throw at it, and the signature written

Re: [Haskell-cafe] Conditional lens

`ifL` isn't a legal lens for several reasons. Lens s t a b generally requires that the types a subsumes b and b subsumes a, and that s subsumes t and t subsumes s. Lens s (Maybe t) (Maybe a) b is a huge red flag. There is an 'illegal prism' provided by lens that is a more principled version of

Re: GHC 7.10 regression when using foldr

There is a limited set of situations where the new signatures can fail to infer, where it would infer before. This can happen when you construct a Foldable/Traversable value using polymorphic tools (like Read) that were previously instantiated for list, but where since foldr et al. are now

Re: GHC 7.10 regression when using foldr

On Tue, Jan 20, 2015 at 9:00 AM, Kim-Ee Yeoh k...@atamo.com wrote: There are few reports because the change hasn't affected the dark majority yet. RC builds are used by a tiny fraction. There's a long tail of users still on 7.6, 7.4, 7.2, and 6.x. We've been actively testing since the

Re: GHC 7.10 regression when using foldr

I was assuming that the list was generated by doing more or less the same check we do now. I haven't looked at the code for it. If so, then it seems it wouldn't flag a now-unnecessary Data.Traversable dependency for instance. At least not without rather significant retooling. I might be off in

Re: GHC 7.10 regression when using foldr

It isn't without a cost. On the down-side, the results of -ddump-minimal-imports would be er.. less minimal. On Tue, Jan 20, 2015 at 6:47 PM, Edward Z. Yang ezy...@mit.edu wrote: I like this proposal: if you're explicit about an import that would otherwise be implicit by Prelude, you

Re: GHC 7.10 regression when using foldr

Sure. Adding it to the CHANGELOG makes a lot of sense. I first found out about it only a few weeks ago when Herbert mentioned it in passing. Of course, the geek in me definitely prefers technical fixes to human ones. Humans are messy. =) I'd be curious how much of the current suite of warnings

Re: GHC 7.10 regression when using foldr

Building -Wall clean across this change-over has a big of a trick to it. The easiest way I know of when folks already had lots of import Data.Foldable import Data.Traversable stuff is to just add import Prelude explicitly to the bottom of your import list rather than painstakingly exclude

Re: Found hole

FWIW- you can think of a 'hole' as a not in scope error with a ton of useful information about the type such a term would have to have in order to go in the location you referenced it. This promotes a very useful style of type-driven development that is common in Agda, where you write out your

Re: Equality Constraints (a ~ b)

They were introduced as part of the System Fc rewrite. The Fc approach has the benefit of unifying a lot of the work on GADTs, functional dependencies, type and data families, etc. all behind the scenes. Every once in a while, (~) constraints can leak into the surface language and it can be

Re: Qualified names in TH?

Using {-# LANGUAGE TemplateHaskell #-} you can use 'foo and ''Foo to get access to the names in scope in the module that is building the splice, rather than worrying about what names are in scope in the module the code gets spliced into. -Edward On Mon, Mar 16, 2015 at 10:54 PM, J. Garrett

Re: -Wall and the fail method

It probably doesn't belong in -Wall, as it is a fairly common idiom to use fail intentionally this way, but it could pretty easily be added to the 'do' and list/monad comprehension desugaring to issue a separate warning that we don't turn on by default. Making it possible to see where you use

Re: Breaking Changes and Long Term Support Haskell

On Wed, Oct 21, 2015 at 8:42 PM, Gregory Collins wrote: > > On Wed, Oct 21, 2015 at 3:18 PM, Geoffrey Mainland > wrote: > >> My original email stated my underlying concern: we are losing valuable >> members of the community not because of the

Re: Breaking Changes and Long Term Support Haskell

On Thu, Oct 22, 2015 at 2:04 AM, Taru Karttunen wrote: > E.g. if > > A) Most of Hackage (including dependencies) compiles with new GHC. > (stack & stackage helps somewhat) > > B) There is an automated tool that can be used to fix most code > to compile with new versions of GHC

Re: Breaking Changes and Long Term Support Haskell

On Thu, Oct 22, 2015 at 1:37 PM, Gregory Collins <g...@gregorycollins.net> wrote: > > On Wed, Oct 21, 2015 at 11:40 PM, Edward Kmett <ekm...@gmail.com> wrote: > >> All I'm saying is that if we want to appeal to or cater to working >>> software engineers, we

Re: [Haskell-cafe] Committee M.O. Change Proposals

The committee was formed from a pool of suggestions supplied to SPJ that represented a fairly wide cross-section of the community. Simon initially offered both myself and Johan Tibell the role of co-chairs. Johan ultimately declined. In the end, putting perhaps too simple a spin on it, the

Re: Breaking Changes and Long Term Support Haskell

all the process indefinitely by raising objections of this form. Such a situation is not without costs all its own. -Edward > Cheers, > Geoff > > > > > On Thu, Oct 22, 2015 at 3:29 PM, Geoffrey Mainland <mainl...@apeiron.net> > wrote: > >

Re: Breaking Changes and Long Term Support Haskell

On Thu, Oct 22, 2015 at 12:20 PM, Mario Blažević wrote: > On 15-10-22 09:29 AM, Geoffrey Mainland wrote: > >> ... >> >> 1) What is the master plan, and where is it documented, even if this >> document is not up to the standard of a proposal? What is the final >> target, and

Re: [Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

On Wed, Oct 7, 2015 at 3:35 AM, Herbert Valerio Riedel wrote: > --8<---cut here---start->8--- > import Control.Applicative as A (Applicative(..)) > > data Maybe' a = Nothing' | Just' a > > instance Functor Maybe' where > fmap f (Just' v) =

Re: [Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

On Tue, Oct 6, 2015 at 3:02 PM, Malcolm Wallace wrote: > > On 6 Oct 2015, at 17:47, Herbert Valerio Riedel wrote: > > At the risk of stating the obvious: I don't think it matters from which > > group a given argument comes from as its validity doesn't depend on the > >

Re: [Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

The part of the MRP proposal that I actively care about because it fixes a situation that *actually causes harm* is moving (>>) to the top level. Why? Right now (*>) and (>>) have different default definitions. This means that code runs often with different asymptotics depending on which one you

Re: [Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

On Tue, Oct 6, 2015 at 1:41 PM, Sven Panne wrote: > 2015-10-06 18:47 GMT+02:00 Herbert Valerio Riedel : > >> [...] That's because -Wall-hygiene (w/o opting out of harmless) warnings >> > across multiple GHC versions is not considered a show-stopper. >> > >

Re: [Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

On Sat, Oct 10, 2015 at 4:12 PM, Yuras Shumovich <shumovi...@gmail.com> wrote: > On Sat, 2015-10-10 at 15:25 -0400, Edward Kmett wrote: > > The part of the MRP proposal that I actively care about because it > > fixes a > > situation that *actually causes harm* is movin

Re: suppress warning "Defined but not used: type variable ‘x’" in GHC-8.0

As a data point I now get thousands of occurrences of this warning across my packages. It is quite annoying. class Foo a where type Bar a instance Foo [a] where type Bar [a] = Int is enough to trigger it. And you can't turn it off by using _ as instance Foo [_] where type Bar [_] = Int

Re: suppress warning "Defined but not used: type variable ‘x’" in GHC-8.0

gt; (At least I think I did that somewhere...) > On Jan 16, 2016 9:24 PM, "Edward Kmett" <ekm...@gmail.com> wrote: > >> As a data point I now get thousands of occurrences of this warning across >> my packages. >> >> It is quite annoying. >>

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