August 2012 - Glasgow-haskell-users

GHC build linking error
by wren ng thornton 30 Nov '12

30 Nov '12

Hello all, I'm working on creating some distribution bundles of GHC 7.4.1 and HP 2012.2.0.0 for OSX 10.5 to help rectify the lack of support on older Macs. In building GHC I've run into a linking error in stage1: ld: duplicate symbol ___gmpz_abs in libraries/integer-gmp/gmp/objs/add.o and libraries/integer-gmp/gmp/objs/abs.o Which looks like the same issue discussed in: http://www.haskell.org/pipermail/glasgow-haskell-users/2011-December/021339… The only proposed solution was Sean mentioned explicitly passing the GMP.framework to ./configure via --with-gmp-libraries and --with-gmp-includes; however, I have no such GMP.framework (I'm building from the framework versions of GHC 6.12.1 and HP 2010.1.0.0). So, any ideas on how to fix this? -- Live well, ~wren

3 3

RULES for ByteString are not fired
by Kazu Yamamoto 28 Oct '12

28 Oct '12

Hello, I seems to us (my friends and me) that term rewriting rules for ByteString are not fired in recent GHCs. 6.12.3 OK 7.0.4 NG 7.4.1 NG 7.6.1RC1 NG For example, with the example from this ticket http://hackage.haskell.org/trac/ghc/ticket/3703 results in as follows: % ghc -O -ddump-simpl-stats --make breakOn.hs 14 RuleFired 4 Class op showsPrec 2 Class op show 2 eqChar#->case 2 unpack 2 unpack-list 1 Class op == 1 Class op >> There is no ByteString rules. Is this a bug or intention? --Kazu {-# LANGUAGE OverloadedStrings #-} import qualified Data.ByteString.Char8 as B main :: IO () main = do let string1 = B.pack "This is a string" string2 = B.pack "This is another string" print (breakOn ' ' string1) print (breakOn ' ' string2) breakOn :: Char -> B.ByteString -> (B.ByteString, B.ByteString) breakOn c = B.break (c==)

3 2

PolyKind issue in GHC 7.6.1rc1: How to make a kind a functional dependency?
by Edward Kmett 12 Oct '12

12 Oct '12

If I define the following {-# LANGUAGE FunctionalDependencies, GADTs, KindSignatures, MultiParamTypeClasses, PolyKinds, RankNTypes, TypeOperators, DefaultSignatures, DataKinds, FlexibleInstances, UndecidableInstances #-} module Indexed.Test where class IMonad (m :: (k -> *) -> k -> *) where ireturn :: a x -> m a x infixr 5 :- data Thrist :: ((i,i) -> *) -> (i,i) -> * where Nil :: Thrist a '(i,i) (:-) :: a '(i,j) -> Thrist a '(j,k) -> Thrist a '(i,k) instance IMonad Thrist where ireturn a = a :- Nil Then 'ireturn' complains (correctly) that it can't match the k with the kind (i,i). The reason it can't is because when you look at the resulting signature for the MPTC it generates it looks like class IMonad k m where ireturn :: a x -> m a x However, there doesn't appear to be a way to say that the kind k should be determined by m. I tried doing: class IMonad (m :: (k -> *) -> k -> *) | m -> k where ireturn :: a x -> m a x Surprisingly (to me) this compiles and generates the correct constraints for IMonad: ghci> :set -XPolyKinds -XKindSignatures -XFunctionalDependencies -XDataKinds -XGADTs ghci> class IMonad (m :: (k -> *) -> k -> *) | m -> k where ireturn :: a x -> m a x ghci> :info IMonad class IMonad k m | m -> k where ireturn :: a x -> m a x But when I add ghci> :{ Prelude| data Thrist :: ((i,i) -> *) -> (i,i) -> * where Prelude| Nil :: Thrist a '(i,i) Prelude| (:-) :: a '(i,j) -> Thrist a '(j,k) -> Thrist a '(i,k) Prelude| :} and attempt to introduce the instance, I crash: ghci> instance IMonad Thrist where ireturn a = a :- Nil ghc: panic! (the 'impossible' happened) (GHC version 7.6.0.20120810 for x86_64-apple-darwin): lookupVarEnv_NF: Nothing Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Moreover, attempting to compile them in separate modules leads to a different issue. Within the module, IMonad has a type that includes the kind k and the constraint on it from m. But from the other module, :info shows no such constraint, and the above code again fails to typecheck, but upon trying to recompile, when GHC goes to load the IMonad instance from the core file, it panicks again differently about references to a variable not present in the core. Is there any way to make such a constraint that determines a kind from a type parameter in GHC 7.6 at this time? I tried the Kind hack used in GHC.TypeLits, but it doesn't seem to be applicable to this situation. -Edward

9 37

Installing binary tarball fails on Linux
by Johan Tibell 09 Oct '12

09 Oct '12

Hi, I tried to install the GHC 7.4.1 32-bit binary tarball today and ran into the error below. Are 32-bit GHC's not supported on 64-bit Linuxes? The error: Installing library in /usr/local/lib/ghc-7.4.1/ghc-prim-0.2.0.0 ghc-cabal: Bad interface file: dist-install/build/GHC/Classes.hi magic number mismatch: old/corrupt interface file? (wanted 33214052, got 129742) Full log: $ tar jxf ghc-7.4.1-i386-unknown-linux.tar.bz2 $ cd ghc-7.4.1/ tibell@tibell:ghc-7.4.1$ ./configure --prefix=/usr/local checking for path to top of build tree... /tmp/ghc-7.4.1 Build platform inferred as: i386-unknown-linux Host platform inferred as: i386-unknown-linux Target platform inferred as: i386-unknown-linux GHC build : i386-unknown-linux GHC host : i386-unknown-linux GHC target : i386-unknown-linux checking for perl... /usr/bin/perl checking if your perl works in shell scripts... yes checking for a BSD-compatible install... /usr/bin/install -c checking whether ln -s works... yes checking for gsed... sed checking for gcc... /usr/bin/gcc checking for gcc... /usr/bin/gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether /usr/bin/gcc accepts -g... yes checking for /usr/bin/gcc option to accept ISO C89... none needed checking version of gcc... 4.4.3 checking how to run the C preprocessor... /usr/bin/gcc -E checking whether ld understands --hash-size=31... checking whether ld understands --reduce-memory-overheads... checking for extra options to pass gcc when compiling via C... -fwrapv checking Setting up CFLAGS, LDFLAGS, IGNORE_LINKER_LD_FLAGS and CPPFLAGS... done checking Setting up CONF_CC_OPTS_STAGE0, CONF_GCC_LINKER_OPTS_STAGE0, CONF_LD_LINKER_OPTS_STAGE0 and CONF_CPP_OPTS_STAGE0... done checking Setting up CONF_CC_OPTS_STAGE1, CONF_GCC_LINKER_OPTS_STAGE1, CONF_LD_LINKER_OPTS_STAGE1 and CONF_CPP_OPTS_STAGE1... done checking Setting up CONF_CC_OPTS_STAGE2, CONF_GCC_LINKER_OPTS_STAGE2, CONF_LD_LINKER_OPTS_STAGE2 and CONF_CPP_OPTS_STAGE2... done checking for .subsections_via_symbols... no checking for GNU non-executable stack support... yes checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking size of void *... 8 checking for ar... /usr/bin/ar checking whether /usr/bin/ar is GNU ar... yes checking for ar arguments... q checking whether ranlib is needed... no configure: creating ./config.status config.status: creating settings config.status: creating mk/config.mk config.status: creating mk/install.mk **************************************************** Configuration done, ready to 'make install' (see README and INSTALL files for more info.) **************************************************** $ sudo make install make -r --no-print-directory -f ghc.mk install BINDIST=YES NO_INCLUDE_DEPS=YES /usr/bin/install -c -m 755 -d "/usr/local/share/man" /usr/bin/install -c -m 755 -d "/usr/local/share/man/man1" /usr/bin/install -c -m 644 docs/man/ghc.1 "/usr/local/share/man/man1" "rm" -f driver/split/dist/ghc-split echo '#!/usr/bin/perl' >> driver/split/dist/ghc-split echo '$TARGETPLATFORM = "i386-unknown-linux";' >> driver/split/dist/ghc-split echo '$TABLES_NEXT_TO_CODE = "YES";' >> driver/split/dist/ghc-split cat driver/split/dist/ghc-split.prl >> driver/split/dist/ghc-split /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 driver/split/dist/ghc-split "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghci-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghci-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghci-7.4.1" echo 'exec "/usr/local/bin/ghc-7.4.1" --interactive ${1+"$@"}' >> "/usr/local/bin/ghci-7.4.1" chmod +x "/usr/local/bin/ghci-7.4.1" "rm" -f "/usr/local/bin/ghci" ln -s ghci-7.4.1 "/usr/local/bin/ghci" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/." && /usr/bin/install -c -m 644 includes/./*.h "/usr/local/lib/ghc-7.4.1/include/./" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts" && /usr/bin/install -c -m 644 includes/rts/*.h "/usr/local/lib/ghc-7.4.1/include/rts/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts/prof" && /usr/bin/install -c -m 644 includes/rts/prof/*.h "/usr/local/lib/ghc-7.4.1/include/rts/prof/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts/storage" && /usr/bin/install -c -m 644 includes/rts/storage/*.h "/usr/local/lib/ghc-7.4.1/include/rts/storage/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/stg" && /usr/bin/install -c -m 644 includes/stg/*.h "/usr/local/lib/ghc-7.4.1/include/stg/" && true /usr/bin/install -c -m 644 includes/ghcautoconf.h includes/ghcplatform.h includes/dist-ghcconstants/header/GHCConstants.h includes/dist-derivedconstants/header/DerivedConstants.h "/usr/local/lib/ghc-7.4.1/include/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include" /usr/bin/install -c -m 644 rts/dist/build/ffi.h rts/dist/build/ffitarget.h "/usr/local/lib/ghc-7.4.1/include/" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/haddock-ghc-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/haddock-ghc-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'exeprog="haddock"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/haddock-ghc-7.4.1" cat utils/haddock/haddock.wrapper >> "/usr/local/bin/haddock-ghc-7.4.1" chmod +x "/usr/local/bin/haddock-ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/latex/" /usr/bin/install -c -m 644 utils/haddock/html/frames.html "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 644 utils/haddock/html/haddock-util.js "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/haskell_icon.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/minus.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/plus.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/xhaddock.css "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/hslogo-16.png "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/minus.gif "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/ocean.css "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/plus.gif "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/synopsis.png "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/latex/haddock.sty "/usr/local/lib/ghc-7.4.1/latex/" "rm" -f "/usr/local/bin/haddock" ln -s haddock-ghc-7.4.1 "/usr/local/bin/haddock" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/hsc2hs" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/hsc2hs" echo '#!/bin/sh' >> "/usr/local/bin/hsc2hs" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/hsc2hs" echo 'exeprog="hsc2hs"' >> "/usr/local/bin/hsc2hs" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/hsc2hs" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/hsc2hs" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/hsc2hs" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/hsc2hs" echo 'HSC2HS_EXTRA="--cflag=-fno-stack-protector "' >> "/usr/local/bin/hsc2hs" cat utils/hsc2hs/hsc2hs.wrapper >> "/usr/local/bin/hsc2hs" chmod +x "/usr/local/bin/hsc2hs" /usr/bin/install -c -m 644 utils/hsc2hs/template-hsc.h "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-pkg-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghc-pkg-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'exeprog="ghc-pkg"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-pkg-7.4.1" cat utils/ghc-pkg/ghc-pkg.wrapper >> "/usr/local/bin/ghc-pkg-7.4.1" chmod +x "/usr/local/bin/ghc-pkg-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-pkg" ln -s ghc-pkg-7.4.1 "/usr/local/bin/ghc-pkg" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/runghc" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/runghc" echo '#!/bin/sh' >> "/usr/local/bin/runghc" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/runghc" echo 'exeprog="runghc"' >> "/usr/local/bin/runghc" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/runghc" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/runghc" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/runghc" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/runghc" cat utils/runghc/runghc.wrapper >> "/usr/local/bin/runghc" chmod +x "/usr/local/bin/runghc" "rm" -f "/usr/local/bin/runhaskell" ln -s runghc "/usr/local/bin/runhaskell" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghc-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghc-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-7.4.1" echo 'exeprog="ghc-stage2"' >> "/usr/local/bin/ghc-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/ghc-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/ghc-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/ghc-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-7.4.1" echo 'executablename="$exedir/ghc"' >> "/usr/local/bin/ghc-7.4.1" cat ghc/ghc.wrapper >> "/usr/local/bin/ghc-7.4.1" chmod +x "/usr/local/bin/ghc-7.4.1" "rm" -f "/usr/local/bin/ghc" ln -s ghc-7.4.1 "/usr/local/bin/ghc" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" for i in driver/ghc-usage.txt driver/ghci-usage.txt rts/dist/build/libHSrts.a rts/dist/build/libHSrts_p.a rts/dist/build/libHSrts-ghc7.4.1.so rts/dist/build/libHSrts_l.a rts/dist/build/libHSrts_debug.a rts/dist/build/libHSrts_thr.a rts/dist/build/libHSrts_thr_debug.a rts/dist/build/libHSrts_thr_l.a rts/dist/build/libHSrts_thr_p.a rts/dist/build/libHSrts_debug-ghc7.4.1.so rts/dist/build/libHSrts_thr-ghc7.4.1.so rts/dist/build/libHSrts_thr_debug-ghc7.4.1.so rts/dist/build/libffi.so rts/dist/build/libffi.so.5 rts/dist/build/libffi.so.5.0.10 settings; do \ case $i in \ *.a) \ /usr/bin/install -c -m 644 $i "/usr/local/lib/ghc-7.4.1"; \ true /usr/local/lib/ghc-7.4.1/`basename $i` ;; \ *.dll) \ /usr/bin/install -c -m 644 -s $i "/usr/local/lib/ghc-7.4.1" ;; \ *.so) \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1" ;; \ *.dylib) \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1";; \ *) \ /usr/bin/install -c -m 644 $i "/usr/local/lib/ghc-7.4.1"; \ esac; \ done /usr/bin/gcc -E -undef -traditional -P -DINSTALLING -DLIB_DIR='"/usr/local/lib/ghc-7.4.1"' -DINCLUDE_DIR='"/usr/local/lib/ghc-7.4.1/include"' -DPAPI_INCLUDE_DIR="" -DPAPI_LIB_DIR="" -x c -Iincludes rts/package.conf.in -o rts/package.conf.install.raw grep -v '^#pragma GCC' rts/package.conf.install.raw | sed -e 's/""//g' -e 's/:[ ]*,/: /g' >rts/package.conf.install /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" for i in utils/haddock/dist/build/tmp/haddock utils/hsc2hs/dist-install/build/tmp/hsc2hs utils/ghc-pkg/dist-install/build/tmp/ghc-pkg utils/runghc/dist-install/build/tmp/runghc ghc/stage2/build/tmp/ghc-stage2; do \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1"; \ done "mv" "/usr/local/lib/ghc-7.4.1/ghc-stage2" "/usr/local/lib/ghc-7.4.1/ghc" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" "rm" -rf "/usr/local/lib/ghc-7.4.1/package.conf.d" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/package.conf.d" "/usr/local/lib/ghc-7.4.1/ghc-pkg" --force --global-conf "/usr/local/lib/ghc-7.4.1/package.conf.d" update rts/package.conf.install Reading package info from "rts/package.conf.install" ... done. "utils/ghc-cabal/dist-install/build/tmp/ghc-cabal" install "/usr/local/lib/ghc-7.4.1/ghc" "/usr/local/lib/ghc-7.4.1/ghc-pkg" "strip" "/usr/local/lib/ghc-7.4.1" libraries/ghc-prim dist-install '' '/usr/local' '/usr/local/lib/ghc-7.4.1' '/usr/local/share/doc/ghc/html/libraries' NO Installing library in /usr/local/lib/ghc-7.4.1/ghc-prim-0.2.0.0 ghc-cabal: Bad interface file: dist-install/build/GHC/Classes.hi magic number mismatch: old/corrupt interface file? (wanted 33214052, got 129742) make[1]: *** [install_packages] Error 1 make: *** [install] Error 2 -- Johan

5 8

Why is Bag's Data instance "broken"?
by Philip Holzenspies 21 Sep '12

21 Sep '12

Dear GHCers, I'm performing traversals over GHC-API results (HsSyn et al). For this purpose, I'm using SYB generics. I found that I couldn't use "ext1Q" for a function with type "Data x => Bag x -> String", i.e. that this function was never applied. The source of Bag's instance of the Data class seems to explain why: instance Data a => Data (Bag a) where gfoldl k z b = z listToBag `k` bagToList b -- traverse abstract type abstractly toConstr _ = abstractConstr $ "Bag("++show (typeOf (undefined::a))++")" gunfold _ _ = error "gunfold" dataTypeOf _ = mkNoRepType "Bag" Is there a rationale to not allow gunfolds and to keep toConstr abstract? More to the point for my needs, is there a reason to not allow dataCast1 casting of Bags? Regards, Philip

3 8

Type operators in GHC
by Simon Peyton-Jones 19 Sep '12

19 Sep '12

Dear GHC users As part of beefing up the kind system, we plan to implement the "Type operators" proposal for Haskell Prime http://hackage.haskell.org/trac/haskell-prime/wiki/InfixTypeConstructors GHC has had type operators for some kind, so you can say data a :+: b = Left a | Right b but you can only do that for operators which start with ":". As part of the above wiki page you can see the proposal to broaden this to ALL operators, allowing data a + b = Left a | Right b Although this technically inconsistent the value page (as the wiki page discussed), I think the payoff is huge. (And "A foolish consistency is the hobgoblin of little minds", Emerson) This email is (a) to highlight the plan, and (b) to ask about flags. Our preferred approach is to *change* what -XTypeOperators does, to allow type operators that do not start with :. But that will mean that *some* (strange) programs will stop working. The only example I have seen in tc192 of GHC's test suite {-# LANGUAGE TypeOperators #-} comp :: Arrow (~>) => (b~>c, c~>d)~>(b~>d) comp = arr (uncurry (>>>)) Written more conventionally, the signature would look like comp :: Arrow arr => arr (arr b c, arr c d) (arr b d) comp = arr (uncurry (>>>)) or, in infix notation {-# LANGUAGE TypeOperators #-} comp :: Arrow arr => (b `arr` c, c `arr` d) `arr` (b `arr` d) comp = arr (uncurry (>>>)) But tc192 as it stands would become ILLEGAL, because (~>) would be a type *constructor* rather than (as now) a type *variable*. Of course it's easily fixed, as above, but still a breakage is a breakage. It would be possible to have two flags, so as to get - Haskell 98 behaviour - Current TypeOperator behaviuor - New TypeOperator behaviour but it turns out to be Quite Tiresome to do so, and I would much rather not. Can you live with that? http://chrisdone.com/posts/2010-10-07-haskelldb-and-typeoperator-madness.ht…

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recent changes to hsc2hs break wrapping c++
by Evan Laforge 09 Sep '12

09 Sep '12

Recently a change was made to hsc2hs to fix this ticket: http://hackage.haskell.org/trac/ghc/ticket/2897 Unfortunately, the result is I (apparently) can't use it now. Here's how that happens: The change was to remove the dependency on HsFFI.h. However, the solution is to create a little wrapper .c file that includes wrappers around various stdio functions like fputs(). This relies on C allowing implicit casts from void* to e.g. FILE*, and is also happy to let you use undeclared functions. g++ rejects that code. And since I am calling into C++ (via a 'extern "C" { ... }' wrapper) I wind up including C++ headers that contain the structs I want hsc2hs to calculate offsets for. Of course one solution is to use C as hsc2hs expects, but it would be awkward to split my (largish) c++ program's headers into C compatible and C++ only. So meanwhile I've reverted back to an older version of hsc2hs that includes HsFFI.h. Working with c++ headers was maybe not in the original design for hsc2hs, but it's a very useful feature nonetheless. WRT HsFFI.h and the ticket, I added -I(ghc --print-libdir)/include to my hsc2hs rule a long time ago, and it wasn't very hard to do, though I admit it would have been easier had there been documentation about what to do, or a mandatory flag for the HsFFI.h path. It looks like Duncan suggested that already. Or perhaps there's a better way to wrap C++?

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Re: Holes in GHC
by Thijs Alkemade 05 Sep '12

05 Sep '12

Hi Simon and others, Yes, an update on our holes in GHC project was very due. What I've been working on: - The command line flag -XHoles and as a language pragma {-# LANGUAGE Holes #-} now work - Holes print a warning message with: - The origin of their type variables - Their local environment - Most of the code has been cleaned up to prepare it for submission as a patch. As an example of the message, consider the module: --- {-# LANGUAGE Holes #-} test x = foldr _ x _ --- This prints: --- [1 of 1] Compiling Main ( test2.hs, interpreted ) test2.hs:3:16: Warning: Found hole `_' with type a0 -> b -> b Where: `b' is a rigid type variable bound by the inferred type of test :: b -> b at test2.hs:3:1 `a0' is a free type variable In scope: x :: b test2.hs:3:20: Warning: Found hole `_' with type [a0] Where: `a0' is a free type variable In scope: x :: b Ok, modules loaded: Main --- The 3 currently remaining issues: - Free type variables are not tidied consistently. For every one of these hole warnings, the same TidyEnv is reused, without taking the updates from the other holes into account. I'm pretty sure I know where this happens and how I could fix it. - What I thought would be the local environment doesn't actually seem to be it. The holes store in their origin the result of `getLclTypeEnv' at their location, but as the Note [Bindings with closed types] says, the TopLevelFlag of these don't actually differentiate the top level from the non-top level bindings. I think it would be more helpful to only show the non-top level bindings at the hole's location, any hints about how to obtain just these would be appreciated. - The holes do not have very accurate source location information, like some other errors have. The hole has its origin, ("test2.hs:3:16"), but somehow not something like: "In the expression: folder _ x _, In an equation for `test': test x = foldr _ x _". Help with how that is supposed to work would also be appreciated. I'm attaching a patch of all my changes compared to HEAD as of about a week ago. All my work can also still be found on https://github.com/xnyhps/ghc. Best regards, Thijs Alkemade

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Small Int and Char closures in GHCi
by Joachim Breitner 31 Aug '12

31 Aug '12

Hi, I am preparing a talk about the details of how data and programs look in memory in Haskell (well, GHC). When explaining the memory consumption of a large String, I wanted to show the effect of short-int-replacement that happens in http://hackage.haskell.org/trac/ghc/browser/rts/sm/Evac.c#L550 I use my ghc-heap-view-package to observe the heap. This programs shows the effect: import GHC.HeapView import System.Mem main = do let hallo = "hallo" mapM_ (\x -> putStrLn $ show x ++ ": " ++ show (asBox x)) hallo performGC mapM_ (\x -> putStrLn $ show x ++ ": " ++ show (asBox x)) hallo gives, as expected: $ ./SmallChar 'h': 0x00007f2811e042a8/1 'a': 0x00007f2811e08128/1 'l': 0x00007f2811e09ef0/1 'l': 0x00007f2811e0bcd8/1 'o': 0x00007f2811e0db10/1 'h': 0x00000000006d9bd0/1 'a': 0x00000000006d9b60/1 'l': 0x00000000006d9c10/1 'l': 0x00000000006d9c10/1 'o': 0x00000000006d9c40/1 but in GHCi, it does not work: $ runhaskell SmallChar.hs 'h': 0x00007f5334623d58/1 'a': 0x00007f5334626208/1 'l': 0x00007f5334627fc0/1 'l': 0x00007f5334629dc0/1 'o': 0x00007f533462bba8/1 'h': 0x00007f533381a1c8/1 'a': 0x00007f5333672e30/1 'l': 0x00007f533381a408/1 'l': 0x00007f533381a6b8/1 'o': 0x00007f533389c5d0/1 Note that the GC does evacuate the closures, as the pointers change. Why are these not replaced by the static ones here? Thanks, Joachim -- Joachim "nomeata" Breitner mail(a)joachim-breitner.de | nomeata(a)debian.org | GPG: 0x4743206C xmpp: nomeata(a)joachim-breitner.de | http://www.joachim-breitner.de/

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ANNOUNCE: GHC 7.6.1 Release Candidate 1
by Ian Lynagh 31 Aug '12

31 Aug '12

We are pleased to announce the first release candidate for GHC 7.6.1: http://www.haskell.org/ghc/dist/7.6.1-rc1/ This includes the source tarball, installers for 32bit and 64bit Windows, and bindists for amd64/Linux, i386/Linux, amd64/OSX and i386/OSX. Please test as much as possible; bugs are much cheaper if we find them before the release! Thanks Ian, on behalf of the GHC team

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