Re: [Haskell-beginners] MonadThrow, MonadReader and shake

14 Dec 2018

      ________________________________________
De : Beginners [beginners-bounces@haskell.org] de la part de Francesco Ariis [fa-ml@ariis.it]
Envoyé : vendredi 14 décembre 2018 13:00
À : beginners@haskell.org
Objet : Re: [Haskell-beginners] MonadThrow, MonadReader and shake

On Fri, Dec 14, 2018 at 11:29:20AM +0000, PICCA Frederic-Emmanuel wrote:
...
src/XdsMe.hs:214:31-52: error:
    • Could not deduce (Control.Monad.Reader.Class.MonadReader
                          Beamline IO)
        arising from a use of ‘toRuchePath’
      from the context: t ~ 'Collect
Are you by chance using existential quantification or gadts?

Yes exactly

data SomeDataCollection where
  SomeDataCollection :: SCollectType t -> SCollectSourceFormat f -> DataCollection t f -> SomeDataCollection

data CollectType = Collect | Caracterization
  deriving Show

data SCollectType a where
  SCollect :: SCollectType 'Collect
  SCaracterization :: SCollectType 'Caracterization

data CollectSourceFormat = Cbf | Hdf5 | Hdf5'
  deriving Show

data SCollectSourceFormat a where
  SCbf :: SCollectSourceFormat 'Cbf
  SHdf5 :: SCollectSourceFormat 'Hdf5
  SHdf5' :: SCollectSourceFormat 'Hdf5'

With All these extensions.

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE UnicodeSyntax #-}

sorry I do not have a public branch with the current modifications.

Cheers

Frederic