On Tue, Oct 20, 2009 at 16:37, Simon Peyton-Jones wrote:

Question: is the template-haskell@haskell.org mailing list still useful?

My gut reaction: probably not.

* It has 250 subscribers compared to 850 for ghc-users. * It has low traffic * template-haskell is the only GHC-specific mailing list associated with a particular language feature. Eg type functions, ghci, etc do not have their own list * The traffic on ghc-users is not dauntingly high.

Also telling is the fact that so many threads are begun and left to rot (i.e. questions remain unanswered). My impression is that very few people actually pay attention to the template-haskell list. I suggest we abolish it in favour of ghc-users. Any dissenters? (I'd emit

a warning, so that people could check they are subscribed to ghc-users.)

Not here. Sean

Thanks for the pointers. Using the GHC API I've managed to extract the names and types of exported functions from other packages (haven't managed to figure out how to extract from the modules in the current package but I'm working on it). I'll post the source code of my "reifyModule" on github once it is cleaned up. First I thought I would examine the source code of template-haskell (more specifically qLocation and qReify) to figure out how to do it but got stuck. Obviously I have still much to learn when it comes to Haskell. Could someone explain how Quasi works? I see: instance Quasi Q where qReify = reify qLocation = location ... instance Quasi IO where qLocation = badIO "currentLocation" qReity = badIO "reify" ... location :: Q Loc location = Q qLocation I guess this means that a Q will ask the embedded Quasi for the location until the Quasi either returns badIO "currentLocation" or ...? The only way this can work (as fast as I can see) is if where is another instance of Quasi than Q and IO but I cannot find that instance in the source code. -- Oscar On Tue, Oct 20, 2009 at 4:38 PM, Simon Peyton-Jones wrote:

[ccing ghc-users]

| I'm trying to extract the names and types of exported functions in a module.

Quite a reasonable request.  But it's not conveniently possible at the moment.  Here's what you can do in the Q monad:

class (Monad m, Functor m) => Quasi m where        -- Fresh names  qNewName :: String -> m Name

       -- Error reporting and recovery  qReport  :: Bool -> String -> m ()    -- Report an error (True) or warning (False)                                        -- ...but carry on; use 'fail' to stop  qRecover :: m a -> m a -> m a         -- Recover from the monadic 'fail'                                        -- The first arg is the error handler

       -- Inspect the type-checker's environment  qReify :: Name -> m Info  qLocation :: m Loc

       -- Input/output (dangerous)  qRunIO :: IO a -> m a

But you want one more function:

 qReifyModule :: String -> m ModuleInfo

where ModuleInfo is something like:

data ModuleInfo = MI { mi_exports :: [Name]                     , ... instances,rules, etc }

Then you could use qReify to get info about a particular thing.

This would not be hard in principle, the details need thought.  For example, if module exports T( C1, C2), where C1, C2 are constructors of T which also has constructors C3, C4, what should appear in mi_exports?  Should mi_exports reflect the structure of the export list (see the AvailInfo type in GHC).

What is the info for an instance? Do we need a way to ask for all the instances of a class (or rules for a function) regardless of what module those instances come from?   etc

Does this ring bells for anyone else?  Would someone like to write the spec?  Are there other reify-related things that we need?

Simon

| -----Original Message----- | From: template-haskell-bounces@haskell.org [mailto:template-haskell- | bounces@haskell.org] On Behalf Of Oscar Finnsson | Sent: 16 October 2009 18:47 | To: template-haskell@haskell.org | Subject: [Template-haskell] How to extract name and type of exported functions in | modules | | Hi, | | I'm trying to extract the names and types of exported functions in a module. | | At the moment I've managed to get a list of all functions in a module | but I can't seem to figure out how to get their types. | | Lets say I got the module | |     module Foo where | |     foo1 :: String -> String |     foo1 value = value | |     foo2 = "hej" | | and then in anothor module... | |     module Bar where | |     bar = $(getAllFunctions "<some-path>/Foo.hs") | | At the moment I got getAllFunctions returning ["foo1","foo2"], but I | would really like to get it to return [("foo1",AppT (ConT "String") | (ConT "String")), ("foo2",ConT "String")] | | Using "parseModuleWithMode" from Language.Haskell.Exts I can get hold | of the names and the type signature of foo1 (since it's specified in | the source code) but I cannot get hold of the type signature of foo2 | (since it's not specified in the source code). | | Is there another way to get the names/signatures of exported functions | from a module other than using parseModuleWithMode so the developer | writing the Foo-module isn't forced to explicitly supply type | signatures of the exported functions? | | If I try "reify" to get information about the functions I get the error message: | "foo1 is not in scope at a reify" | | This seems to be a known bug about reify (reported here | http://hackage.haskell.org/trac/ghc/ticket/2339). My problem is that I | cannot use the workaround since I don't know the name of the | functions. | | Another disadvantage with this approach is that "getAllFunctions" must | have access to the source code of the module and that I must supply | the path the the module. If possible I would like to have code such as | |     bar = $(getAllFunctions "Foo") | | instead of "<come-path>/Foo.hs". | | Regards, | Oscar Finnsson | _______________________________________________ | template-haskell mailing list | template-haskell@haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell