- Glasgow-haskell-users

Avoid blank line separating code and comments in Bird style?
by R Sidhu 15 Jan '15

15 Jan '15

Hi This regarding GHC behaviour for literate Haskell programs in Bird style. GHC expects a blank line between comment[1] and code. Otherwise, during the literate pre-processor stage, the error 'unlit: Program line next to comment' is reported. While above behaviour makes sense in general, there are situations where one would like to place comments adjacent to code with no intervening blank line. For example, in documenting a declaration using Haddock (in standard, non-literate Haskell), as shown in sections 3.1 <https://www.haskell.org/haddock/doc/html/markup.html#idm140354810917952> and 3.2 <http://www.haskell.org/haddock/doc/html/ch03s02.html> of the Haddock User Guide, no blank line separates comment and code. Any way to enable GHC to accept Bird style literate programs with no blank lines separating comment and code? [1] 'Comment' (in context of Bird style) refers to text on lines not beginning with '>'. Regards Sidhu

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Future of the boxes package--call for ideas
by David Feuer 13 Jan '15

13 Jan '15

I've just taken over maintainership of the boxes package, and will be making a maintenance release shortly (as soon as I figure out how and get added to the maintainers group). The package, however, currently suffers from a paucity of bug reports (no problem) and feature requests (not so great). To keep things lively, I need a bit of help from two groups of people. If you use the package but wish it could do something more for you, I want to know about it. If you considered using the package but rejected it because it couldn't quite handle your job, I want to know about that too. I'd prefer if people would open issues and pull requests at https://github.com/treeowl/boxes/issues but I will also accept requests by email. Thanks, David

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conflicting multi-parameter family instance declarations
by Michal Konečný 13 Jan '15

13 Jan '15

Dear all, The following compiles with ghc 7.6 but fails with ghc 7.8: ----- {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} module Test where class M t s where type T t s data I t = I t instance M t t where type (T t t) = () instance M t (I t) where type (T t (I t)) = () ----- The error I get with ghc 7.8.3 and 7.8.4 is: Test.hs:12:10: Conflicting family instance declarations: T t t -- Defined at Test.hs:12:10 T t (I t) -- Defined at Test.hs:15:10 I am curious if this change is an improvement or a bug. I would be grateful for help as this issue affects a fairly large library I develop. Best regards, Michal -- |-| Dr. Michal Konecny, Computer Science, Aston University |-| Room MB212D | Tel +44 121 204 3462 | Fax +44 121 204 3681 |-| http://duck.aston.ac.uk/konecnym |-| OpenPGP key http://duck.aston.ac.uk/konecnym/ki.aston

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ANNOUNCE: GHC version 7.8.4
by Austin Seipp 13 Jan '15

13 Jan '15

============================================================== The (Interactive) Glasgow Haskell Compiler -- version 7.8.4 ============================================================== The GHC Team is pleased to announce a new patchlevel release of GHC, 7.8.4. This is an important bugfix release relative to 7.8.3 (with over 30 defects fixed), so we highly recommend upgrading from the previous 7.8 releases. The full release notes are here: https://downloads.haskell.org/~ghc/7.8.4/docs/html/users_guide/release-7-8-… How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: https://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://ghc.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: http://ghc.haskell.org/trac/ghc/wiki/Platforms http://ghc.haskell.org/trac/ghc/wiki/CodeOwners Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://ghc.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: http://ghc.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug Hashes & Signatures ~~~~~~~~~~~~~~~~~ On https://downloads.haskell.org/~ghc/7.8.4/ you will find a signed copy of the SHA256 hashes for the tarballs, using my GPG key (keyid 0x3B58D86F). -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Equality Constraints (a ~ b)
by Dominic Steinitz 12 Jan '15

12 Jan '15

Hi, I am trying to find more background on these. They don’t exist in the Haskell 2010 Language Report, they didn’t exist in ghc 6.8.2 but make an appearance in 7.0.1. The documentation in the manual is rather sparse and doesn’t contain a reference: https://downloads.haskell.org/~ghc/latest/docs/users_guide.pdf section 7.11. Folk on #ghc referred me to http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/. I can find papers that refer to ~ in F_C (aka FC?) but as far as I can tell not in the Haskell language itself. Many thanks Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

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Compiling a cabal project with LLVM on GHC 7.10 RC1
by Brandon Simmons 07 Jan '15

07 Jan '15

I've tried: $ cabal install --only-dependencies -w /usr/local/bin/ghc-7.10.0.20141222 --enable-tests --enable-benchmarks --ghc-option=-fllvm --ghc-option=-static $ cabal configure -w /usr/local/bin/ghc-7.10.0.20141222 --enable-tests --enable-benchmarks --ghc-option=-fllvm --ghc-option=-static $ cabal build Building foo-0.3.0.0... Preprocessing library foo-0.3.0.0... when making flags consistent: Warning: Using native code generator rather than LLVM, as LLVM is incompatible with -fPIC and -dynamic on this platform I don't see anything referencing "PIC" in the output of cabal build -v. I can build a hello world program, just fine with `ghc --make`: $ /usr/local/bin/ghc-7.10.0.20141222 --make -O2 -fllvm Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... Thanks, Brandon

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Changes to the type checker with respect to UndecidableInstances
by Mitsutoshi Aoe 06 Jan '15

06 Jan '15

Hi, I found a difference between GHC 7.6.3 and 7.8.3 with respect to UndecidableInstances. https://gist.github.com/maoe/57a4346eb36aee159916 <https://gist.github.com/maoe/57a4346eb36aee159916> 7.6.3 requires UndecidableInstances to compile this snippet whereas 7.8.3 doesn't. What has changed in the type checker? Mitsutoshi

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ANNOUNCE: GHC 7.10.1 Release Candidate 1
by Austin Seipp 06 Jan '15

06 Jan '15

We are pleased to announce the first release candidate for GHC 7.10.1: https://downloads.haskell.org/~ghc/7.10.1-rc1/ This includes the source tarball and bindists for 64bit/32bit Linux and Windows. Binary builds for other platforms will be available shortly. (CentOS 6.5 binaries are not available at this time like they were for 7.8.x). These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x3B58D86F). We plan to make the 7.10.1 release sometime in February of 2015. We expect another RC to occur during January of 2015. Please test as much as possible; bugs are much cheaper if we find them before the release! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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install-strip
by harry 06 Jan '15

06 Jan '15

Trying to build 7.8.4 from the source distribution (linux). make install-strip should work as per trac #1851, and the target does indeed appear in distrib/Makefile. However, the build uses the top-level Makefile, which doesn't, leading to # make install-strip ===--- building phase 0 make -r --no-print-directory -f ghc.mk phase=0 phase_0_builds make[1]: Nothing to be done for `phase_0_builds'. ===--- building phase 1 make -r --no-print-directory -f ghc.mk phase=1 phase_1_builds make[1]: Nothing to be done for `phase_1_builds'. ===--- building final phase make -r --no-print-directory -f ghc.mk phase=final install-strip make[1]: *** No rule to make target `install-strip'. Stop. make: *** [install-strip] Error 2 Am I doing something wrong? -- View this message in context: http://haskell.1045720.n5.nabble.com/install-strip-tp5763372.html Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.

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What to do when garbage collector is slow?
by David Spies 05 Jan '15

05 Jan '15

I have a program that, to all appearances, is behaving properly. It uses very little memory to run, it has the profile I would expect looking at +RTS -hc. I have no reason to believe there is a memory leak (in the sense that it's not lazily holding on to things it no longer needs or strictly generating things it doesn't need yet). But it's slow, and according to -sstderr, most of the time is spent garbage-collecting. Why is the garbage-collector consuming so much running time? How can I deal with it? The program is a solution to this problem: https://open.kattis.com/problems/tourist The input data can be found here: http://heim.ifi.uio.no/~db/nm-i-programmering/nm2004/testdata/h.in

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