Re: [Haskell-cafe] Dynamically typing TH.Exp at runtime
Sorry, maybe it I didn't made it clear enough. Perhaps I'm misunderstanding something, but since one can infer types in GHCI, that implies one can infer types in the GHC API; since Hint wraps the GHC API, that implies one can infer types in Hint, doesn't it? And indeed, there are functions to infer the type of a String; iirc I've even used them myself in mueval. That's true, inferring the type of a string is not the problem. However, I am not only interested in the top-level type, but also in the type of any arbitrary subexpression. Consider for example following recursive definition: foo [] = [] foo (x:xs) = (:)(x+1)(foo xs) Typing only the first rule one would says its type is '[a] - [a]'. However, the second rule specialises the type to 'Num a = [a] - [a]'. So, if I am interested in the type of the 'x' in the pattern of the second rule, I need to be aware of its binding on the right-hand side. Consequently the type of 'x' is 'Num a'. AFAIK, I need Hendley-Milner type inference for that (please correct me if I am wrong) and I was wondering if I really need to implement it by myself, when it is already somewhere inside GHC. Thanks, Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Dynamically typing TH.Exp at runtime
On 2009 Mar 13, at 4:03, Martin Hofmann wrote: That's true, inferring the type of a string is not the problem. However, I am not only interested in the top-level type, but also in the type of any arbitrary subexpression. Consider for example following recursive definition: I'm pretty sure you can pull a typed AST out of ghc-api and query the type of any node. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Dynamically typing TH.Exp at runtime
I am doing meta-programming at runtime. So my program gets a full Haskell declaration in expression quotation ([d|...|]) modifies it and returns the modified expression. Therefore, I need type information of this expression, and any subexpression, at _runtime_ ! For example: [d| reverse x1 = y1 |] - rewrites_to - [d| reverse x2:xs = y2:ys |] - rewrites_to - [d| reverse x:xs = reverse xs ++ [x] |] reverse :: [a] - [a] implies x2,y2 :: a x1,y1,xs,ys :: [a] TH.reify is not applicable, because I need the information at runtime and I am in IO. I suppose Data.Dynamic does not work either, because [| xs|] :: ExpQ and not [a]. So it looks like I need my own type checker and inference and tag each subexpression with its type. If so, I can even omit TH and use my own data type for the abstract syntax tree. This annoys me a bit, because for me it seems that all I need is already there. Did anybody have similar problems, because I shouldn't be the only one doing dynamic typing in a static language? Is there a Haskell implementation of the paper Typing Dynamic Typing by Baars and Swierstra (http://people.cs.uu.nl/arthurb/dynamic.html ), so I can try out if this helps me? Any help, comments, and how-to-suggestions are highly welcome. Thanks a lot, Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Dynamically typing TH.Exp at runtime
This is what hint does, isn't it? However, this still leaves it to me to infer what type [|a|] in [| reverse (a:b:[]) = (b:a:[]) |] is. Thanks a lot anyway. Martin On Thu, 2009-03-12 at 12:59 -0200, Daniel Gorín wrote: would using ghc-as-a-library to type (strings with) haskell expressions at runtime help? On Mar 12, 2009, at 12:37 PM, Martin Hofmann wrote: I am doing meta-programming at runtime. So my program gets a full Haskell declaration in expression quotation ([d|...|]) modifies it and returns the modified expression. Therefore, I need type information of this expression, and any subexpression, at _runtime_ ! For example: [d| reverse x1 = y1 |] - rewrites_to - [d| reverse x2:xs = y2:ys |] - rewrites_to - [d| reverse x:xs = reverse xs ++ [x] |] reverse :: [a] - [a] implies x2,y2 :: a x1,y1,xs,ys :: [a] TH.reify is not applicable, because I need the information at runtime and I am in IO. I suppose Data.Dynamic does not work either, because [| xs|] :: ExpQ and not [a]. So it looks like I need my own type checker and inference and tag each subexpression with its type. If so, I can even omit TH and use my own data type for the abstract syntax tree. This annoys me a bit, because for me it seems that all I need is already there. Did anybody have similar problems, because I shouldn't be the only one doing dynamic typing in a static language? Is there a Haskell implementation of the paper Typing Dynamic Typing by Baars and Swierstra (http://people.cs.uu.nl/arthurb/dynamic.html ), so I can try out if this helps me? Any help, comments, and how-to-suggestions are highly welcome. Thanks a lot, Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
