Maybe TypeFamilies would work for you? I can only give you a
barebones outline of what it might look like.
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, TypeFamilies #-}
import Control.Monad.Trans.Maybe
data DataFrameH5 a = DataFrameH5
data DataFrameH5Path = DataFrameH5Path
class Frame t where
type Key t
len :: t -> IO (Maybe Int)
row :: t -> Int -> MaybeT IO (Key t)
instance Frame (DataFrameH5 a) where
type Key (DataFrameH5 a) = a
len DataFrameH5 = return . Just $ undefined
row DataFrameH5 idx = MaybeT $ do
return undefined
On Wed, Feb 22, 2017 at 10:27 AM, PICCA Frederic-Emmanuel
Hello, I wrote this code
data DataFrameH5 a = DataFrameH5 (Nxs a) -- Nexus file (DataSource H5) -- gamma (DataSource H5) -- delta (DataSource H5) -- wavelength PoniGenerator -- ponie generator
class Frame t a where len :: t -> IO (Maybe Int) row :: t -> Int -> MaybeT IO (DifTomoFrame a DIM1)
instance Frame (DataFrameH5 DataFrameH5Path) DataFrameH5Path where len (DataFrameH5 _ _ (DataSourceH5 _ d) _ _) = lenH5Dataspace d
row d@(DataFrameH5 nxs' g d' w ponigen) idx = do n <- lift $ len d let eof = fromJust n - 1 == idx let mu = 0.0 let komega = 0.0 let kappa = 0.0 let kphi = 0.0 gamma <- g `atIndex'` (ix1 0) delta <- d' `atIndex'` (ix1 idx) wavelength <- w `atIndex'` (ix1 0) let source = Source (head wavelength *~ nano meter) let positions = concat [mu, komega, kappa, kphi, gamma, delta] -- print positions let geometry = Geometry K6c source positions Nothing let detector = ZeroD m <- lift $ geometryDetectorRotationGet geometry detector poniext <- lift $ ponigen (MyMatrix HklB m) idx return $ DifTomoFrame { difTomoFrameNxs = nxs' , difTomoFrameIdx = idx , difTomoFrameEOF = eof , difTomoFrameGeometry = geometry , difTomoFramePoniExt = poniext }
has you can see my t type contains also the a reference to the a one So when I create the instance, I need to write two times the DataFrameH5Path
I would like to know how to write the same class with only
class Frame t where len :: t -> IO (Maybe Int) row :: t -> Int -> MaybeT IO (DifTomoFrame <extract type a from type t> DIM1)
thanks for your help
Frederic _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners