- Glasgow-haskell-users

capabilities of GHC API
by Frederik Eaton 22 May '07

22 May '07

Hello, I think what I'm trying to do is too ambitious, but I thought I would ask to see if it is possible. It seems like there is no easy way to do it, given what I've seen of the GHC API. I would like to have a function, say it is called "this", which has the following effect in ghci > let n = 2 in this > n 2 In other words, it captures all the variables which are in scope, and adds them to the GHCi environment. Somebody helpful will probably say "But you can just write 'let n = 2'!", but that is not the aim. There are several aims. One is to be able to look at the variables inside a function which one is trying to debug, then inserting 'this' will cause them to be in scope, I think that would be useful. A more important aim is to be able to use existentially quantified variables easily. Currently I can do: > reifyIntegral 5 (\n -> print $ reflectNum n) 5 but how can I get GHCi to have an 'n' binding which is inside the function? Clearly just returning 'n' will not work: > reifyIntegral 5 id <interactive>:1:0: Inferred type is less polymorphic than expected ... This is what I am thinking of doing, but as I said it seems ambitious. There are several easier things one could think of: > let n = 2 in bind "n" n > n 2 If it were possible to add bindings to the GHCi bindings list, then this would be easy. Is it possible? The documentation doesn't seem to mention such a capability. Also, probably another useful feature would be to combine 'this' with something in the IO monad: > withProgName "blah" thisIO > getProgName "blah" So, are these things currently possible? Planned? Have the functions I describe been implemented already? I think there is a GHCi debugger in the works, so maybe functionality like this will be part of it, I didn't want to start something on my own if that is the case... Many thanks, Frederik -- http://ofb.net/~frederik/

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Wanted: warning option for usages of unary minus
by Isaac Dupree 22 May '07

22 May '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Since the unary negation operator `-' is often considered a wart in Haskell's syntax and in many cases saying "negate" is arguably clearer anyway, I propose adding options to GHC to warn about its use. The only case I don't normally want to be warned about is "negative numeric literals", e.g. (-1), even if in current Haskell they do mean (negate (fromInteger 1)) not (fromInteger (negate 1)) (or equivalently, (fromInteger (negate (fromInteger 1))) as the inner fromInteger === id). I know this would be useful to someone since I caught myself manually cleaning some of my code in this way without the help of warning messages :) Proposed flag names and descriptions (could use a little tidying up) : - -fwarn-unary-minus Causes a warning to be emitted for all usages of the unary operator `-', except those in which its argument is a numeric literal that is not separated from the minus sign by any space (space includes comments). - -fwarn-all-unary-minus For those who hate it with a passion, this option warns about ALL uses of the unary `-' operator, even code like `(-1)'. Opinions? (Should I put a feature request in Trac? Is that what I perhaps should have done in the first place?) Is this simple enough to try to implement myself so I can start getting to know GHC's internals? (I suspect that detecting the adjacency of the "-" to a numeric literal without changing the actual precedence may be a little tricky... -2^6 parses as negate(2^6) and should get a warning, as should (- 2), IMO) Oh, the actual warning message... file:line:column: Warning: Unary minus in expression foo (or, on the next line, In the expression: foo ?) for an appropriate "foo", which has parentheses added to describe the effects of operator precedence, as usual for GHC diagnostic messages (it's just particularly important for making this one easy to understand in some cases) Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGGBpSHgcxvIWYTTURAt5sAKCEIohHMiuUy9AofhWKzvDOf4rwmgCeJcbj e2RmW+UX2E6omuLpFfIH9fs= =1SnR -----END PGP SIGNATURE-----

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How to to terminate runStmt in "GHC as a library"
by Mads Lindstrøm 21 May '07

21 May '07

Hi all I am trying to build a GUI for GHCi using "GHC as a library". See http://haskell.org/haskellwiki/GHC/As_a_library . One requirement is that the GUI is still responsive when executing code using GHC.runStmt. Therefore I do: forkIO $ GHC.runStmt someStatement >> return() While this works fine, it does give me one problem. How do I terminate a call to runStmt prematurely? One would think that this would work: threadId <-forkIO $ GHC.runStmt someStatement >> return() ... killThread threadId However, as runStmt also uses forkIO internally I am not killing the thread that runs "someStatement" - actually nothing seems to happen when executing the action "killThread threadId". Anybody knows how to kill the thread running "someStatement"? I have attached a more complete program which illustrates the problem described above. I have only tested the program on Debian/Linux. Greetings, Mads Lindstrøm

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optimization that doesn't make recompilation be needed more often?
by Isaac Dupree 21 May '07

21 May '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Could there be a flag weaker than -O that doesn't cause recompilation any more than -O0 does -- would that provide any worthwhile optimizations? (an intermediate speed-tradeoff option for haskell developers.) Dependency on the details of modules never expected to be recompiled (e.g. base library, or any package not currently being compiled, but those are just heuristics) should be fine. Wondering, Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGTh/PHgcxvIWYTTURAk6bAJwJm9p9A2z2oyRdHd3YsqmEGdd7MQCfd7LV E3FgIi+XUZNsRlzgxKPhIGI= =OzsN -----END PGP SIGNATURE-----

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ghc stackfaults
by John Meacham 21 May '07

21 May '07

ghc 6.6 and 6.6.1 both go into infinite loops and eventually die with a stackfault when trying to compile the attached file with optimizations turned on. -- John Meacham - ⑆repetae.net⑆john⑈

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integrating ghc as editor's code tools
by Paulo Henrique 19 May '07

19 May '07

I´m trying to integrated ghc and Crimson editor (Windows), to get a small and efficient package. I found how to integrate ghc and JCreator, but the package has more than 100MB. I configured Crimson's Tools -> Preferences->User Tools with this values: Menu text: GHC Command: C:\ghc\ghc-6.6.1\bin\ghc.exe (or C:\ghc\ghc-6.6.1\bin\ghci).exe Argument: $(FileName) Initial Dir: $[FileDir] Hot Key: no one and I have choose "Capture Output". After wite and save a test file, I called the ghc tool. the answe I get was: -with ghc: ---------- Capture Output ---------- > "C:\ghc\ghc-6.6.1\bin\ghc.exe" FirstTeste.hs > Terminated with exit code 0. with ghci: ---------- Capture Output ---------- > "C:\ghc\ghc-6.6.1\bin\ghci.exe" FirstTeste.hs > Terminated with exit code 0. How can I solve this problem? If anyone has a better solution (another editor), I would like to know it. thanks in advance, Paulo Henrique

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Re: GNUreadline.framework and GMP.framework
by Christian Maeder 19 May '07

19 May '07

It seems our GMP.framework is only suited for Powerpc. I'll look after it. Thanks for your hints and sorry for the inconveniences. (Meanwhile you could try to get the GMP.framework for intel macs from elsewhere.) Christian P.S. There is also a problem with the GNUreadline.framework in your home directory on Powerpcs only. When you link your own binaries you have to add -optl-F$(HOME)/Library/Frameworks -optl-framework -optlGNUreadline to ghc's command line. Jay McCarthy schrieb: > Your frameworks: > > I've made binary distributions for powerpc and intel macs that rely on a > GNUreadline.framework and a GMP.framework that can be found (for both > architectures) here: > > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > > Do not work on Intel: > > jay $ wget > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > --09:37:01-- > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > => `GNUreadline-framework.zip' > Resolving www.informatik.uni-bremen.de... 134.102.224.5 > Connecting to www.informatik.uni-bremen.de|134.102.224.5|:80... connected. > HTTP request sent, awaiting response... 200 OK > Length: 2,342,369 (2.2M) [application/zip] > > 100%[====================================>] 2,342,369 345.15K/s > ETA 00:00 > > 09:37:10 (264.54 KB/s) - `GNUreadline-framework.zip' saved > [2342369/2342369] > > ~/Desktop > jay $ wget > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > --09:37:12-- > http://www.informatik.uni-bremen.de/agbkb/forschung/formal_methods/CoFI/het… > > => `GMP.framework.zip' > Resolving www.informatik.uni-bremen.de... 134.102.224.5 > Connecting to www.informatik.uni-bremen.de|134.102.224.5|:80... connected. > HTTP request sent, awaiting response... 200 OK > Length: 564,957 (552K) [application/zip] > > 100%[====================================>] 564,957 228.26K/s > > 09:37:15 (227.77 KB/s) - `GMP.framework.zip' saved [564957/564957] > > ~/Desktop > jay $ unzip GNUreadline-framework.zip -d $HOME/Library/Frameworks > Archive: GNUreadline-framework.zip > creating: /Users/jay/Library/Frameworks/GNUreadline.framework/ > creating: /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/ > creating: /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/ > creating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/ > creating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/ > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/rltypedefs.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/chardefs.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/keymaps.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/history.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/tilde.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/rlstdc.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/rlconf.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/Headers/readline/readline.h > > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/Versions/A/GNUreadline > linking: /Users/jay/Library/Frameworks/GNUreadline.framework/GNUreadline > -> Versions/A/GNUreadline > linking: /Users/jay/Library/Frameworks/GNUreadline.framework/Headers > -> Versions/A/Headers > creating: /Users/jay/Library/Frameworks/GNUreadline.framework/info/ > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/info/readline.info > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/info/rluserman.info > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/info/history.info > inflating: /Users/jay/Library/Frameworks/GNUreadline.framework/info/dir > inflating: /Users/jay/Library/Frameworks/GNUreadline.framework/README > inflating: /Users/jay/Library/Frameworks/GNUreadline.framework/COPYING > inflating: /Users/jay/Library/Frameworks/GNUreadline.framework/CHANGELOG > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/build-framework-R.sh > inflating: > /Users/jay/Library/Frameworks/GNUreadline.framework/readline-5.2.tar.gz > finishing deferred symbolic links: > /Users/jay/Library/Frameworks/GNUreadline.framework/GNUreadline -> > Versions/A/GNUreadline > /Users/jay/Library/Frameworks/GNUreadline.framework/Headers -> > Versions/A/Headers > ~/Desktop > jay $ unzip GMP.framework.zip -d $HOME/Library/Frameworks > Archive: GMP.framework.zip > creating: /Users/jay/Library/Frameworks/GMP.framework/ > inflating: /Users/jay/Library/Frameworks/GMP.framework/build-framework.sh > inflating: /Users/jay/Library/Frameworks/GMP.framework/ChangeLog > inflating: /Users/jay/Library/Frameworks/GMP.framework/COPYING.LIB > linking: /Users/jay/Library/Frameworks/GMP.framework/GMP -> > Versions/A/GMP > linking: /Users/jay/Library/Frameworks/GMP.framework/Headers -> > Versions/A/Headers > creating: /Users/jay/Library/Frameworks/GMP.framework/info/ > inflating: /Users/jay/Library/Frameworks/GMP.framework/info/gmp.info > inflating: /Users/jay/Library/Frameworks/GMP.framework/info/gmp.info-1 > inflating: /Users/jay/Library/Frameworks/GMP.framework/info/gmp.info-2 > inflating: /Users/jay/Library/Frameworks/GMP.framework/README > creating: /Users/jay/Library/Frameworks/GMP.framework/Versions/ > creating: /Users/jay/Library/Frameworks/GMP.framework/Versions/A/ > inflating: /Users/jay/Library/Frameworks/GMP.framework/Versions/A/GMP > creating: /Users/jay/Library/Frameworks/GMP.framework/Versions/A/Headers/ > inflating: > /Users/jay/Library/Frameworks/GMP.framework/Versions/A/Headers/gmp.h > finishing deferred symbolic links: > /Users/jay/Library/Frameworks/GMP.framework/GMP -> Versions/A/GMP > /Users/jay/Library/Frameworks/GMP.framework/Headers -> Versions/A/Headers > ~/Desktop > jay $ ghc > dyld: Library not loaded: GMP.framework/Versions/A/GMP > Referenced from: > /Users/jay/Development/dists/ghc/ghc-6.6.1/lib/i386-apple-darwin/ghc-6.6.1 > Reason: no suitable image found. Did find: > /Users/jay/Library/Frameworks/GMP.framework/Versions/A/GMP: > mach-o, but wrong architecture > Trace/BPT trap > ~/Desktop > jay $ >

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Re: Wanted: warning option for usages of unary minus
by John Meacham 19 May '07

19 May '07

On Thu, May 17, 2007 at 06:40:04PM +0200, Twan van Laarhoven wrote: > Simon Marlow wrote: > >... > > > >Really? I'm beginning to have second thoughts about the proposed change > >to negation for Haskell'. The main reason, and this isn't pointed out > >as well as it should be on the wiki, is that "x-1" will cease to be an > >infix application of (-), it will parse as x applied to the literal > >(-1). And this is different from "x - 1" > > There is one other alternative for parsing: > "-" is a unary minus if and only if it is > a) preceded by whitespace or one of "[({;,", and > b) not followed by whitespace. > > So: > x - 1 == (-) x 1 > x-1 == (-) x 1 > x -1 == x (negate 1) > x -(1) == x (negate 1) > x (-1) == x (negate 1) > x (- 1) == x (\y -> y - 1) also (c) has a digit after it. also note that a big point of this is that we can get rid of 'negate' in the translation, so the literal -1 now desugars to (fromInteger -1) rather than the current (negate (fromInteger 1)) (which requires 2 dictionary lookups for a simple constant! sigh. we also have the option of removing negate from the 'Num' class if so desired. John -- John Meacham - ⑆repetae.net⑆john⑈

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Libraries makefile
by Stefan Holdermans 17 May '07

17 May '07

I noticed that the makefile in ghc/libraries is changed recently--- could it be broken? When building GHC HEAD on Mac OS X (Darwin, Power PC), I got: ... make -C libraries boot rm -f -rf bootstrapping.Cabal cp -R Cabal bootstrapping.Cabal bootstrapping.Cabal $ -name "*.o" -o -name "*.hi" $ \ -exec rm -f -f {} \; /bin/sh: line 1: bootstrapping.Cabal: command not found make[1]: *** [stamp/bootstrapping.Cabal] Error 127 make: *** [stage1] Error 2

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Re: Wanted: warning option for usages of unary minus
by Isaac Dupree 17 May '07

17 May '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Twan van Laarhoven wrote: > There is one other alternative for parsing: > "-" is a unary minus if and only if it is > a) preceded by whitespace or one of "[({;,", and > b) not followed by whitespace. > > So: > x - 1 == (-) x 1 > x-1 == (-) x 1 > x -1 == x (negate 1) > x -(1) == x (negate 1) > x (-1) == x (negate 1) > x (- 1) == x (\y -> y - 1) > > Just an idea. Indeed, and in some language syntax designs it would certainly be a good system for prefix operators. Existing parsers may have some difficulty. How about > {-comment-}-1 ? how about > WeirdNumber{value=2,weird=True}-1 ? Although likely to make any actual code work, it seems a bit complicated from the mindset of current Haskell parsing/lexing. "(b) not followed by whitespace." can be replaced by (b) followed by a digit if desired not to allow it for negating arbitrary expressions. Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGTJRgHgcxvIWYTTURAqpMAJ9rpCFwzOG/ZSF0qpM/hD/mFKrQ1wCfSRCK 2nKiBzRs/8thmgrdBT+SowA= =lFCl -----END PGP SIGNATURE-----

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