Hello Brian,
Tuesday, August 22, 2006, 1:16:08 AM, you wrote:
The solution seems to be something like:
$(extend_data [d|
data D = X {f::Int, g::String}
|])
$(extend_instance [d|
instance Obj D where
...
|])
or just
Hi,
I'm starting to explore Template Haskell and I've got the following program:
-- almost directly from Template meta-programming in Haskell paper
module Duma.Template.Test
( Format(..)
, printf
) where
import Language.Haskell.TH
Hello Brian,
[snip]
getInfo :: Q Info
getInfo = reify (mkName Car)
[snip]
-- Crashes if I try to print out the info
-- info - runQ getInfo
-- putStrLn (pprint info)
[snip]
The example from the paper works fine with the few minor
Hello Brian,
Monday, August 21, 2006, 6:34:06 PM, you wrote:
-- almost directly from Template meta-programming in Haskell paper
i should warn you that some TH details was changed in 6.4. these
changes described in second TH paper and afair, reifying is among them
look at
Bulat Ziganshin wrote:
Hello Brian,
Monday, August 21, 2006, 6:34:06 PM, you wrote:
-- almost directly from Template meta-programming in
Haskell paper
i should warn you that some TH details was changed in 6.4. these
changes described in second TH paper and afair, reifying is among
Arie Peterson wrote:
I seem to remember that 'reify' cannot be run in the IO monad. IIRC
ghci gives a nice error message saying this, so perhaps you can try
to execute 'main' from within ghci to corroborate my suspicion.
Yes you're right - ghci gives the error:
Can't do `reify' in the IO
Hello Arie,
Monday, August 21, 2006, 7:08:31 PM, you wrote:
getInfo :: Q Info
getInfo = reify (mkName Car)
-- Crashes if I try to print out the info
-- info - runQ getInfo
I seem to remember that 'reify' cannot be run in the IO monad.
oh, yes! runQ
Bulat Ziganshin wrote:
as you can see, it don't supports reification, recovery and
information about currently compiled module just because there is no
such information when program runs. and of course, you can't add new
fields or new functions at run-time. isntead typical technique is:
