May 2003 - template-haskell

RE: [Template-haskell] Release
by Simon Marlow 23 May '03

23 May '03

> | > > * Use a naming scheme for the functions that avoids having > | > > to suffix some with "E" or "D" and some not. Example: we > | > > have "cond", but "letE". Better *uniformly* use a single > | > > suffix for all functions of the same class; eg, "condExp" > | > > and "letExp" (or "condE" and "letE" if you desperately > | > > want to save letters). > > I'm sorry that I didn't respond to this at the time. I agree with the > first sentence, but I had not absorbed the full glory of making every > single constructor three or four characters longer. Like Tim, I don't > think this is a good plan. We don't say JustMaybe and NothingMabye. > Instead, we just choose constructor names that don't clash within a > particular module. (Between unrelated modules, we can rely > on qualified names etc.) We need to decide what naming scheme is going to be in GHC 6.0. I already merged through Ian's renaming changes, so the current situation is that GHC 6.0 has the longer names. Time is short, so I could just back out to the previous story if there's no concensus. Cheers, Simon

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RE: [Template-haskell] Release
by Simon Peyton-Jones 23 May '03

23 May '03

| As I understand it the GHC team are heading towards a release including | TH in the not too distant future. I think it would be good if the | biggest outstanding issues could be fixed before then (and indeed, just | fixed ASAP). Yes, that's a good idea. | The one that causes me the most hoop jumping is the type parameters to | some of the TH datastructures. For example, I have some code like this: It's all to do with Tim's "two-level types" scheme, but I do agree with you that it seems more trouble than its worth. Tim: how vigorously do you want to defend this? If not, can we let Ian remove the parameterisation? Simon | -----Original Message----- | From: template-haskell-admin(a)haskell.org [mailto:template-haskell- | admin(a)haskell.org] On Behalf Of Ian Lynagh | Sent: 08 April 2003 13:17 | To: template-haskell(a)haskell.org | | | As I understand it the GHC team are heading towards a release including | TH in the not too distant future. I think it would be good if the | biggest outstanding issues could be fixed before then (and indeed, just | fixed ASAP). | | The one that causes me the most hoop jumping is the type parameters to | some of the TH datastructures. For example, I have some code like this: | | class ToDec a where | to_dec :: a -> Dec | | instance ToDec Dec where | to_dec = id | | class ToExp a where | to_exp :: a -> Exp | | instance ToExp Exp where | to_exp = id | | instance (ToExp e, ToDec d) => Foo (Match p e d) where | foo (Mat p (Normal e) ds) = bar (Normal (Let (map to_dec ds) (to_exp e))) | | Which I'd much rather be able to write as | | instance Foo Match where | foo (Mat p (Normal e) ds) = bar (Normal (Let (map to_dec ds) (to_exp e))) | | Previous discussions about this have all petered out before reaching a | conclusion, but I haven't seen anyone actually stand up and defend the | parameterised types, and it's hard to see how they could be useful | without everything being parameterised anyway. Can we get rid of them? | Please? Or at least have an explanation of why not... | | Hmmm, or maybe I should be asking for them to be extended to cover all | the types to make it easier to have a type of reification that annotates | the tree with type and strictness information. I'd still have the | problem above, but at least more things would be possible. | | Anyway, I'm confused, but sitting in the middle is just driving me mad! | | | Thanks | Ian | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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Dec type is missing "NewType"
by Andre Pang 21 May '03

21 May '03

Hi all, I think the Dec data type in THSyntax.hs (starting at line 174) is missing the "newtype" declaration. It currently looks like this: data Dec = Fun String [Clause] -- { f p1 p2 = b where decs } | Val Pat RightHandSide [Dec] -- { p = b where decs } | Data Cxt String [String] [Con] [String] -- { data Cxt x => T x = A x | B (T x) deriving (Z,W)} | TySyn String [String] Typ -- { type T x = (x,x) } | Class Cxt String [String] [Dec] -- { class Eq a => Ord a where ds } | Instance Cxt Typ [Dec] -- { instance Show w => Show [w] where ds } | Proto String Typ -- { length :: [a] -> Int } | Foreign Foreign deriving( Show ) Am I missing something, or is no way to write a newtype declaration? I presume it's not the same as either a TySyn or Data. Thanks once again, -- % Andre Pang : trust.in.love.to.save

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RE: [Template-haskell] Calling foreign functions in a splice doesn't work
by Simon Peyton-Jones 19 May '03

19 May '03

OK, I reckon I've fixed this. You can now specify any extra C libraries on the command line (c_double.o), and they'll get linked if any TH runs happen. Simon | -----Original Message----- | From: template-haskell-admin(a)haskell.org [mailto:template-haskell-admin@haskell.org] On Behalf Of | André Pang | Sent: 12 May 2003 16:14 | To: template-haskell(a)haskell.org | Cc: chak(a)cse.unsw.edu.au | Subject: [Template-haskell] Calling foreign functions in a splice doesn't work | | Hi all, | | I've been trying to call a foreign function (i.e. via the FFI) inside a | splice, which doesn't seem to work. | | As an example, I'll attach a small program which does work, and then | modify it so it doesn't work. So, here's a program which does work: | | Splicer.hs: | | > module Main where | > | > import Templates | > | > main :: IO () | > main = do | > putStrLn (show ($(doubleWrapper) 5)) | | Templates.hs: | | > module Templates where | > | > import Language.Haskell.THSyntax | > | > doubleWrapper :: Expr | > doubleWrapper = [| \x -> myDouble x |] | > | > myDouble :: Int -> Int | > myDouble x = x * 2 | | Pretty simple: the program splices in an Expr named doubleWrapper; | doubleWrapper in turn calls myDouble, which is a simple function of | type Int -> Int. Execution: | | > 20:10 ~/th/ffi-bug % ghc -fglasgow-exts --make Splicer.hs | > ... | > 20:10 ~/th/ffi-bug % ./a.out | > 10 | | So that works. | | Here's a version of the program which modifies the 'myDouble' function | so that it's now a foreign C function rather than a Haskell function. | (Note that the main function and doubleWrapper functions are exactly | the same): | | SplicerFFI.hs: | | > module Main where | > | > import TemplatesFFI | > | > main :: IO () | > main = do | > putStrLn (show ($(doubleWrapper) 5)) | | TemplatesFFI.hs: | | > module TemplatesFFI where | > | > import Language.Haskell.THSyntax | > | > doubleWrapper :: Expr | > doubleWrapper = [| \x -> myDouble x |] | > | > foreign import ccall safe "c_double.h myDouble" | > myDouble :: Int -> Int | | c_double.h: | | > int myDouble (int x); | | c_double.c: | | > int myDouble (int x) | > { | > return x * 2; | > } | | Compiling the FFI version of this small program doesn't work: | | > 20:20 ~/th/ffi-bug % gcc -c c_double.c | > 20:20 ~/th/ffi-bug % ghc -fglasgow-exts --make c_double.o | > SplicerFFI.hs c_double.o | > Chasing modules from: SplicerFFI.hs | > Compiling TemplatesFFI ( TemplatesFFI.hs, ./TemplatesFFI.o ) | > Compiling Main ( SplicerFFI.hs, ./SplicerFFI.o ) | > Loading package base ... linking ... done. | > Loading package haskell98 ... linking ... done. | > Loading package haskell-src ... linking ... done. | > | > TemplatesFFI.o: unknown symbol `_myDouble' | > | > SplicerFFI.hs:7: | > Exception when trying to run compile-time code: | > Code: doubleWrapper | > Exn: | > In the first argument of `show', namely | > `($[splice]doubleWrapper 5)' | > In the first argument of `putStrLn', namely | > `(show ($[splice]doubleWrapper 5))' | > In the result of a 'do' expression: | > putStrLn (show ($[splice]doubleWrapper 5)) | | I suspect the compilation isn't working because the 'myDouble' symbol | in c_double.o isn't being loaded _at splice time_ into the list of | symbols that GHC knows about -- which is also why the exception occurs. | I've tried all sorts of kludges to convince GHC to load the symbol | from the foreign object file, like doing "ar rcs libcdouble.a | c_double.o" and then putting -L. -lcdouble on the commandline, passing | additional linker/compiler flags with -optl and -optc, etc, and none of | them have worked so far. | | This was tested with GHC on Mac OS X built from CVS 9 March 2003; my | apologies for a fairly out-of-date GHC build, but I'm having trouble | building the recent GHCs on Mac OS X. Can somebody verify that this | also occurs on Linux with a recent build of GHC, and hopefully fix it | or give me a clue on where to start looking for the bug? | | Thanks very much! | | | -- | % Andre Pang : just.your.average.bounty.hunter | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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RE: [Template-haskell] Splicing in class declarations doesn't work
by Simon Peyton-Jones 19 May '03

19 May '03

Fixed, thank you. Simon | -----Original Message----- | From: template-haskell-admin(a)haskell.org [mailto:template-haskell-admin@haskell.org] On Behalf Of | Andre Pang | Sent: 17 May 2003 18:41 | To: template-haskell(a)haskell.org | Subject: [Template-haskell] Splicing in class declarations doesn't work | | Hallo all, | | I think I've found a bug with declaring classes, or more specifically, | declaring functions which instances of the classes are required to | implement. Splicing in the following code works fine: | | spliceTest = [d| class Foo f where {} |] | | However, splicing in this code doesn't work: | | spliceTestDeux = [d| class Bar b where { baz :: Int -> Int } |] | | 3:30 ~/th/newnew % ghci -fglasgow-exts -ddump-splices | ObjCTypesTHTest.hs | ... | ObjCTypesTHTest.hs:1: Splicing declarations | spliceTest ======> class Foo f'0 | ObjCTypesTHTest.hs:1: Splicing declarations | spliceTestDeux | ======> | class Bar b'1 where { baz :: GHC.Base.Int -> GHC.Base.Int; } | | Variable not in scope: `baz' | | Misplaced type signature: baz :: Int -> Int | Failed, modules loaded: ObjCTypesTH. | *ObjCTypesTH> | | Splicing in a "raw" declaration: | | spliceTestDeux :: Q [Dec] | spliceTestDeux = return | [ Class [] "Bar" ["b"] [Proto "baz" (tappsArr [intCon, intCon])] ] | where | intCon = Tcon (TconName "Int") | | doesn't work either (with exactly the same error message). | | (BTW, should I send TH-related bugs to template-haskell, put them in | the bug tracker, or both?) | | Thanks again, | | | -- | % Andre Pang : trust.in.love.to.savee | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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RE: [Template-haskell] Dec type is missing "NewType"
by Simon Peyton-Jones 19 May '03

19 May '03

Yes, that's true. No deep reason. Ian: would you feel up to adding newtype declarations, since you are Mr THSyntax? Thanks Simon | -----Original Message----- | From: template-haskell-admin(a)haskell.org [mailto:template-haskell-admin@haskell.org] On Behalf Of | Andre Pang | Sent: 17 May 2003 15:14 | To: template-haskell(a)haskell.org | Subject: [Template-haskell] Dec type is missing "NewType" | | Hi all, I think the Dec data type in THSyntax.hs (starting at line 174) | is missing the "newtype" declaration. It currently looks like this: | | data Dec | = Fun String [Clause] -- { f p1 p2 = b where decs } | | Val Pat RightHandSide [Dec] -- { p = b where decs } | | Data Cxt String [String] | [Con] [String] -- { data Cxt x => T x = A x | | B (T x) deriving (Z,W)} | | TySyn String [String] Typ -- { type T x = (x,x) } | | Class Cxt String [String] [Dec] -- { class Eq a => Ord a where | ds } | | Instance Cxt Typ [Dec] -- { instance Show w => Show | [w] where ds } | | Proto String Typ -- { length :: [a] -> Int } | | Foreign Foreign | deriving( Show ) | | Am I missing something, or is no way to write a newtype declaration? I | presume it's not the same as either a TySyn or Data. | | Thanks once again, | | | -- | % Andre Pang : trust.in.love.to.save | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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Splicing in class declarations doesn't work
by Andre Pang 17 May '03

17 May '03

Hallo all, I think I've found a bug with declaring classes, or more specifically, declaring functions which instances of the classes are required to implement. Splicing in the following code works fine: spliceTest = [d| class Foo f where {} |] However, splicing in this code doesn't work: spliceTestDeux = [d| class Bar b where { baz :: Int -> Int } |] 3:30 ~/th/newnew % ghci -fglasgow-exts -ddump-splices ObjCTypesTHTest.hs ... ObjCTypesTHTest.hs:1: Splicing declarations spliceTest ======> class Foo f'0 ObjCTypesTHTest.hs:1: Splicing declarations spliceTestDeux ======> class Bar b'1 where { baz :: GHC.Base.Int -> GHC.Base.Int; } Variable not in scope: `baz' Misplaced type signature: baz :: Int -> Int Failed, modules loaded: ObjCTypesTH. *ObjCTypesTH> Splicing in a "raw" declaration: spliceTestDeux :: Q [Dec] spliceTestDeux = return [ Class [] "Bar" ["b"] [Proto "baz" (tappsArr [intCon, intCon])] ] where intCon = Tcon (TconName "Int") doesn't work either (with exactly the same error message). (BTW, should I send TH-related bugs to template-haskell, put them in the bug tracker, or both?) Thanks again, -- % Andre Pang : trust.in.love.to.savee

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RE: [Template-haskell] Splicing in a TypQ == parse error?
by Simon Peyton-Jones 14 May '03

14 May '03

| How do you splice in a type in Template Haskell? The quasi-quote | notation seems to work succesfully, but attempting to splice it gives | me a parse error: At the moment you can't. See http://haskell.org/pipermail/template-haskell/2003-February/000021.html I'd like to solve that. Tim is visiting next week, so we'll be discussing it. Meanwhile, do others have opinions? Simon

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Splicing in a TypQ == parse error?
by Andre Pang 14 May '03

14 May '03

Hi all, How do you splice in a type in Template Haskell? The quasi-quote notation seems to work succesfully, but attempting to splice it gives me a parse error: MyTypes.hs: module MyTypes where import Language.Haskell.THSyntax stringType = [t| String |] SpliceType.hs: module SpliceType where import Language.Haskell.THSyntax foo :: $(stringType) -> $(stringType) foo x = x ++ "foo" Compiling it: 18:28[18] ~/th/new % ghc -fglasgow-exts SpliceType.hs SpliceType.hs:7: parse error on input `$(' The same happens if I try to to write "data Foo = Foo $(stringType)" in SpliceType.hs. Am I getting the syntax wrong, or is splicing types not implemented yet? I'm using a May 13, 2003 build of GHC. Merci, -- % Andre Pang : trust.in.love.to.save

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Calling foreign functions in a splice doesn't work
by André Pang 13 May '03

13 May '03

Hi all, I've been trying to call a foreign function (i.e. via the FFI) inside a splice, which doesn't seem to work. As an example, I'll attach a small program which does work, and then modify it so it doesn't work. So, here's a program which does work: Splicer.hs: > module Main where > > import Templates > > main :: IO () > main = do > putStrLn (show ($(doubleWrapper) 5)) Templates.hs: > module Templates where > > import Language.Haskell.THSyntax > > doubleWrapper :: Expr > doubleWrapper = [| \x -> myDouble x |] > > myDouble :: Int -> Int > myDouble x = x * 2 Pretty simple: the program splices in an Expr named doubleWrapper; doubleWrapper in turn calls myDouble, which is a simple function of type Int -> Int. Execution: > 20:10 ~/th/ffi-bug % ghc -fglasgow-exts --make Splicer.hs > ... > 20:10 ~/th/ffi-bug % ./a.out > 10 So that works. Here's a version of the program which modifies the 'myDouble' function so that it's now a foreign C function rather than a Haskell function. (Note that the main function and doubleWrapper functions are exactly the same): SplicerFFI.hs: > module Main where > > import TemplatesFFI > > main :: IO () > main = do > putStrLn (show ($(doubleWrapper) 5)) TemplatesFFI.hs: > module TemplatesFFI where > > import Language.Haskell.THSyntax > > doubleWrapper :: Expr > doubleWrapper = [| \x -> myDouble x |] > > foreign import ccall safe "c_double.h myDouble" > myDouble :: Int -> Int c_double.h: > int myDouble (int x); c_double.c: > int myDouble (int x) > { > return x * 2; > } Compiling the FFI version of this small program doesn't work: > 20:20 ~/th/ffi-bug % gcc -c c_double.c > 20:20 ~/th/ffi-bug % ghc -fglasgow-exts --make c_double.o > SplicerFFI.hs c_double.o > Chasing modules from: SplicerFFI.hs > Compiling TemplatesFFI ( TemplatesFFI.hs, ./TemplatesFFI.o ) > Compiling Main ( SplicerFFI.hs, ./SplicerFFI.o ) > Loading package base ... linking ... done. > Loading package haskell98 ... linking ... done. > Loading package haskell-src ... linking ... done. > > TemplatesFFI.o: unknown symbol `_myDouble' > > SplicerFFI.hs:7: > Exception when trying to run compile-time code: > Code: doubleWrapper > Exn: > In the first argument of `show', namely > `($[splice]doubleWrapper 5)' > In the first argument of `putStrLn', namely > `(show ($[splice]doubleWrapper 5))' > In the result of a 'do' expression: > putStrLn (show ($[splice]doubleWrapper 5)) I suspect the compilation isn't working because the 'myDouble' symbol in c_double.o isn't being loaded _at splice time_ into the list of symbols that GHC knows about -- which is also why the exception occurs. I've tried all sorts of kludges to convince GHC to load the symbol from the foreign object file, like doing "ar rcs libcdouble.a c_double.o" and then putting -L. -lcdouble on the commandline, passing additional linker/compiler flags with -optl and -optc, etc, and none of them have worked so far. This was tested with GHC on Mac OS X built from CVS 9 March 2003; my apologies for a fairly out-of-date GHC build, but I'm having trouble building the recent GHCs on Mac OS X. Can somebody verify that this also occurs on Linux with a recent build of GHC, and hopefully fix it or give me a clue on where to start looking for the bug? Thanks very much! -- % Andre Pang : just.your.average.bounty.hunter

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