-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I have got a little further by defining the following functions and I now have a better defined question.
- --Takes a list and converts it to a n-ary tuple - --i.e. Generates functions like [String] -> (a,a,a) listToTuple i = lam [Pvar "xs"] (tup ([ infixE (Just $ var "xs") (var "!!") (Just $ lit (Integer n)) | n <- [0..(i-1)] ])) - --Casts an n-ary tuple of type (String,String,..) - --i.e. Generates functions like (a,a,a) -> (Int,Bool,Int) cast i = lam [Ptup pats] (tup [ app (var "read") v | v <- vars]) where pats = [ Pvar $ show n | n <- [1..i] ] vars = [ var $ show n | n <- [1..i] ] So, I can now define a function f, f :: [String] -> (Int, Bool) f = $(cast 2) . $(listToTuple 2) but I can still see no way to infer the size of the tuple purely from the declared type signature. Tom On Wed, 2 Jul 2003 11:56 am, Thomas L. Bevan wrote: > Hi, > > I'm struggling to write the following function in Template Haskell. > > I have a phantom type, > > >data HTMLPage a = HTMLPage FilePath > > This type points to an HTML file, where 'a' refers to the return type of > the posted form. > So, mostly, I would expect types like > HTMLPage (String, String, Date, Int) > > Where this represented a form the returned someone's first name, last name, > dob and age. > > So, I want a function that will take the returned name/value pairs and cast > them into the matching type. > > eg. > > >readForm :: Read a => [(String,String)] -> HTMLPage a -> a > > Can anyone give me any pointers or am I better off just abandoning this > approach? > > Tom > > _______________________________________________ > Haskell mailing list > [EMAIL PROTECTED] > http://www.haskell.org/mailman/listinfo/haskell -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) iD8DBQE/AvOlYha8TWXIQwoRAju7AKCxXxFQ1gMLTIUt93UpXyIQRVdqMQCg0Ryo FQK/bFrjQaV9fOyi6naeYEo= =fuyq -----END PGP SIGNATURE----- _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
