March 2014 - Glasgow-haskell-users

importing (<=) from GHC.TypeLits
by Henning Thielemann 17 Mar '14

17 Mar '14

I want to import Nat and type-level (<=) from GHC.TypeLits: import GHC.TypeLits (Nat, (<=)) "Nat" is found this way, but (<=) is not: Module ‘GHC.TypeLits’ does not export ‘(<=)’ What is the trick? The doc only shows the anonymous import: http://www.haskell.org/ghc/docs/7.8.1-rc2/html/users_guide/promotion.html

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type-level induction on Nat
by Henning Thielemann 17 Mar '14

17 Mar '14

Am 16.03.2014 09:40, schrieb Christiaan Baaij: > To answer the second question (under the assumption that you want > phantom-type style Vectors and not GADT-style): That works, someNatVal was the missing piece. Now the natural next question is how to perform type-level induction on Nat. This page mentions the Nat1 type, a unary representation of natural numbers: https://ghc.haskell.org/trac/ghc/wiki/TypeNats/MatchingOnNats Since the unary natural number kind so ubiquituous in examples, is there a recommended module to import it from, which also contains the injectivity magic of FromNat1? I cannot see it in: http://hackage.haskell.org/package/base-4.7.0.0/candidate/docs/GHC-TypeLits… although it seems to have been there: http://co-dan.github.io/base-docs/src/GHC-TypeLits.html

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splicing varPs in quasi-quote brackets
by Christian Höner zu Siederdissen 17 Mar '14

17 Mar '14

Hello everybody, I wrote me this nice function 'buildRns' which splices in $(varP w) nice and recursively. Unfortunately, this only seems to work in the 7.8 branch, not in 7.6.3. Is this indeed new, or am I missing something obvious? The message is: ADP/Fusion/TH.hs:106:86: Parse error in pattern: $(varP w) The code works wonderfully in 7.8. It not only compiles, but also produces working code in applications. I have no problem waiting until 7.8 is stable, but being backwards compatible to 7.6 would be nice. Many thanks, Christian buildRns f xs [] = appE ([| return . SM.singleton |]) (foldl (\g z -> appE g (varE z)) (return f) xs) buildRns f xs (VarP v : ys) = buildRns f (xs++[v]) ys buildRns f xs (TupP [_,VarP v] : ys) = do w <- newName "w" [| $(varE v) >>= return . SM.concatMapM (\ $(varP w) -> $(buildRns f (xs++[w]) ys)) |] -->>>>> ^^^^^^^^^

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GHC-7.8 warning on rules that may not fire
by Henning Thielemann 17 Mar '14

17 Mar '14

With GHC-7.8 I get lots of warnings like src/Foo/Bar.hs:215:6: Warning: Rule "foo" may never fire because ‘bar’ might inline first Probable fix: add an INLINE[n] or NOINLINE[n] pragma on ‘bar’ So far I thought that rewrite RULES always have precedence to INLINE. Has this changed? I hesitate to follow the advice of adding phase numbers in bracket because I consider these phase numbers a quite fragile and non-modular solution (like precedence numbers for infix operators). I have found: https://ghc.haskell.org/trac/ghc/wiki/Plugins/Phases Is this still considered for future developments?

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Safe Haskell trust
by Fabian Bergmark 17 Mar '14

17 Mar '14

Im using the Hint library in a project where users are able to upload and run code. As I don't want them to do any IO, I run the interpreter with -XSafe. However, some packages (in my case aeson) are needed and I therefore tried marking them as trusted with ghc-pkg trust aeson. This seems to have no effect however and the interpreter fails with: Data.Aeson: Can't be safely imported! The module itself isn't safe Is there any way to get XSafe-like guarantees with the ability of allowing certain packages?

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SV: PROPOSAL: Literate haskell and module file names
by Niklas Larsson 17 Mar '14

17 Mar '14

I tested and it works on Windows. Niklas ----- Ursprungligt meddelande ----- Från: "Brandon Allbery" <allbery.b(a)gmail.com> Skickat: ‎2014-‎03-‎17 14:22 Till: "Edward Kmett" <ekmett(a)gmail.com> Kopia: "glasgow-haskell-users(a)haskell.org" <glasgow-haskell-users(a)haskell.org>; "haskell-prime(a)haskell.org Prime" <haskell-prime(a)haskell.org> Ämne: Re: PROPOSAL: Literate haskell and module file names On Mon, Mar 17, 2014 at 9:08 AM, Edward Kmett <ekmett(a)gmail.com> wrote: Foo+rst.lhs does nicely dodge the collision with jhc. Is this legal on Windows? -- brandon s allbery kf8nh sine nomine associates allbery.b(a)gmail.com ballbery(a)sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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Re: positive type-level naturals
by Henning Thielemann 16 Mar '14

16 Mar '14

Am 16.03.2014 13:48, schrieb Dan Frumin: > This is just a wild guess, but is there a possibility that (1+n) will > produce less complaints than (n+1)? unfortunately no

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RC2 build failure on Debian: armhf
by Joachim Breitner 15 Mar '14

15 Mar '14

Hi, armhf still fails like in RC1: https://buildd.debian.org/status/fetch.php?pkg=ghc&arch=armhf&ver=7.8.20140… [..] 0% ( 0 / 5) in 'WwLib' 0% ( 0 / 2) in 'DmdAnal' 0% ( 0 / 2) in 'WorkWrap' compiler/typecheck/TcSplice.lhs-boot:29:1: TcSplice.tcTopSpliceExpr is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:37:1: TcSplice.runMetaE is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:38:1: TcSplice.runMetaP is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:39:1: TcSplice.runMetaT is exported by the hs-boot file, but not exported by the module compiler/typecheck/TcSplice.lhs-boot:40:1: TcSplice.runMetaD is exported by the hs-boot file, but not exported by the module 67% ( 2 / 3) in 'CmmPipeline' 0% ( 0 / 3) in 'StgCmmHpc' 0% ( 0 / 13) in 'PrelInfo' 0% ( 0 / 4) in 'StgCmmCon' 0% ( 0 / 2) in 'StgCmmExpr' 0% ( 0 / 6) in 'StgCmmBind' 0% ( 0 / 2) in 'CmmParse' 0% ( 0 / 2) in 'StgCmm' 5% ( 9 /175) in 'TcRnMonad' make[2]: *** [compiler/stage2/doc/html/ghc/ghc.haddock] Error 1 Any ideas? Anyone feeling responsible? Thanks, Joachim -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0x4743206C Debian Developer: nomeata(a)debian.org

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Problem with cabal's --enable-library-coverage on 7.8.1rc2
by Federico Mastellone 14 Mar '14

14 Mar '14

Hi, On Mac OS X 10.9.2 with ghc 7.8.0.20140228 and cabal 1.18.0.3 Doing: cabal configure --enable-library-coverage cabal build Fails with: > ld: illegal text reloc in '_enablezmlibraryzmcoveragezm0zi0zi1_Library_sendMsg2_info' to '__hpc_tickboxes_enablezmlibraryzmcoveragezm0zi0zi1_Util_hpc' for architecture x86_64 > clang: error: linker command failed with exit code 1 (use -v to see invocation) But without the coverage flag it’s OK. I found it when switching from 7.6.3 to 7.8.1RC2 on a project I have and was able to strip it to this: https://github.com/fmaste/ghc-7.8.0.20140228-enable-library-coverage Don’t know if this is a cabal or ghc problem and I don’t know how to continue. Thanks! My ghc —info: [("Project name","The Glorious Glasgow Haskell Compilation System") ,("GCC extra via C opts"," -fwrapv") ,("C compiler command","/usr/bin/gcc") ,("C compiler flags"," -m64 -fno-stack-protector") ,("C compiler link flags"," -m64") ,("ld command","/usr/bin/ld") ,("ld flags"," -arch x86_64") ,("ld supports compact unwind","YES") ,("ld supports build-id","NO") ,("ld supports filelist","YES") ,("ld is GNU ld","NO") ,("ar command","/usr/bin/ar") ,("ar flags","clqs") ,("ar supports at file","NO") ,("touch command","touch") ,("dllwrap command","/bin/false") ,("windres command","/bin/false") ,("libtool command","libtool") ,("perl command","/usr/bin/perl") ,("target os","OSDarwin") ,("target arch","ArchX86_64") ,("target word size","8") ,("target has GNU nonexec stack","False") ,("target has .ident directive","True") ,("target has subsections via symbols","True") ,("Unregisterised","NO") ,("LLVM llc command","llc") ,("LLVM opt command","opt") ,("Project version","7.8.0.20140228") ,("Booter version","7.6.3") ,("Stage","2") ,("Build platform","x86_64-apple-darwin") ,("Host platform","x86_64-apple-darwin") ,("Target platform","x86_64-apple-darwin") ,("Have interpreter","YES") ,("Object splitting supported","YES") ,("Have native code generator","YES") ,("Support SMP","YES") ,("Tables next to code","YES") ,("RTS ways","l debug thr thr_debug thr_l thr_p dyn debug_dyn thr_dyn thr_debug_dyn l_dyn thr_l_dyn") ,("Support dynamic-too","YES") ,("Support parallel --make","YES") ,("Dynamic by default","NO") ,("GHC Dynamic","YES") ,("Leading underscore","YES") ,("Debug on","False") ]

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RC2 build failure on Debian: armel
by Joachim Breitner 12 Mar '14

12 Mar '14

Hi, armel still fails like in RC1: https://buildd.debian.org/status/fetch.php?pkg=ghc&arch=armel&ver=7.8.20140… "inplace/bin/ghc-stage2" -o utils/haddock/dist/build/tmp/haddock ... /«PKGBUILDDIR»/compiler/stage2/build/libHSghc-7.8.0.20140228.a(genSym.o): In function `genSym': genSym.c:(.text+0x84): undefined reference to `arm_atomic_spin_lock' genSym.c:(.text+0x88): undefined reference to `arm_atomic_spin_unlock' Any ideas? Anyone feeling responsible? Thanks, Joachim -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0x4743206C Debian Developer: nomeata(a)debian.org

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