haskell-jp / questions #66

sNatToNat' :: Sing n -> Sing (ConvertNat n)
sNat'ToNat :: Sing (ConvertNat n) -> Sing n

readCSV :: WrapForall Csv.FromField Vector xs => FilePath -> IO (RecordOf Vector xs)
readCSV filepath = do
    csvBs <- BL.readFile filepath
    case Csv.decode Csv.HasHeader csvBs :: Either String (Vector (Record xs)) of
        Left reason -> error reason
        Right vs -> undefined

....hs:36:82: error:
    • Expected kind '[membership-0:Type.Membership.Internal.Assoc
                        k0 *]',
        but 'xs' has kind '[*]'
    • In the second argument of 'RecordOf', namely 'xs'
      In the first argument of 'IO', namely '(RecordOf Vector xs)'
      In the type signature:
        readCSV :: WrapForall Csv.FromField Vector xs =>
                   FilePath -> IO (RecordOf Vector xs)
   |
36 | readCSV :: WrapForall Csv.FromField Vector xs => FilePath -> IO (RecordOf Vector xs)
   |   

{-# LANGUAGE PolyKinds #-}

....hs:30:125: error:
    • Expected kind '[membership-0:Type.Membership.Internal.Assoc
                        * *]',
        but 'xs' has kind '[membership-0:Type.Membership.Internal.Assoc
                              ghc-prim-0.5.3:GHC.Types.Symbol *]'
    • In the first argument of 'DataFrame', namely 'xs'
      In the first argument of 'IO', namely '(DataFrame xs)'
      In the type signature:
        readCSV :: Forall (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs =>
                   FilePath -> IO (DataFrame xs)

readCSV :: Forall (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs => FilePath -> IO (RecordOf Vector xs)
readCSV filepath = do
    csvBs <- BL.readFile filepath
    case Csv.decode Csv.HasHeader csvBs :: Either String (Vector (Record xs)) of
        Left reason -> error reason
        Right vs -> undefined

...hs:52:10: error:
    • Could not deduce (Forall
                          (Instance1 Csv.FromField (Field Identity)) xs1)
        arising from a use of 'Csv.decode'
      from the context: Forall
                          (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs
        bound by the type signature for:
                   readCSV :: forall (xs :: [membership-0:Type.Membership.Internal.Assoc
                                               ghc-prim-0.5.3:GHC.Types.Symbol *]).
                              Forall
                                (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs =>
                              FilePath -> IO (RecordOf Vector xs)
        at src/Data/Frame/Reader.hs:49:1-115
    • In the expression:
          Csv.decode Csv.HasHeader csvBs ::
            Either String (Vector (Record xs))
      In a stmt of a 'do' block:
        case  Csv.decode Csv.HasHeader csvBs ::
                Either String (Vector (Record xs))
        of
          Left reason -> error reason
          Right vs -> undefined
      In the expression:
        do csvBs <- BL.readFile filepath
           case  Csv.decode Csv.HasHeader csvBs ::
                   Either String (Vector (Record xs))
           of
             Left reason -> error reason
             Right vs -> undefined
   |
52 |     case Csv.decode Csv.HasHeader csvBs :: Either String (Vector (Record xs)) of
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeOperators #-}

module Data.Frame.Reader where

import qualified Data.ByteString.Lazy as BL

import qualified Data.Csv as Csv
import Data.Extensible 
import Data.Vector (Vector)

readCSV :: forall xs. Forall (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs => FilePath -> IO (RecordOf Vector xs)
readCSV filepath = do
    csvBs <- BL.readFile filepath
    case Csv.decode Csv.HasHeader csvBs :: Either String (Vector (Record xs)) of
        Left reason -> error reason
        Right vs -> undefined

.hs:19:10: error:
    • Could not deduce (Forall
                          (Instance1 Csv.FromField (Field Identity)) xs)
        arising from a use of 'Csv.decode'
      from the context: Forall
                          (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs
        bound by the type signature for:
                   readCSV :: forall (xs :: [Assoc
                                               ghc-prim-0.5.3:GHC.Types.Symbol *]).
                              Forall
                                (KeyValue KnownSymbol (Instance1 Csv.FromField Vector)) xs =>
                              FilePath -> IO (RecordOf Vector xs)
        at src/Data/Frame/Reader.hs:16:1-126
    • In the expression:
          Csv.decode Csv.HasHeader csvBs ::
            Either String (Vector (Record xs))
      In a stmt of a 'do' block:
        case  Csv.decode Csv.HasHeader csvBs ::
                Either String (Vector (Record xs))
        of
          Left reason -> error reason
          Right vs -> undefined
      In the expression:
        do csvBs <- BL.readFile filepath
           case  Csv.decode Csv.HasHeader csvBs ::
                   Either String (Vector (Record xs))
           of
             Left reason -> error reason
             Right vs -> undefined

readCSV :: forall xs. Forall (KeyValue KnownSymbol (Instance1 Csv.FromField Identity)) xs => FilePath -> IO (RecordOf Vector xs)
readCSV filepath = do
    csvBs <- BL.readFile filepath
    case Csv.decodeByName csvBs :: Either String (Csv.Header, Vector (Record xs)) of
        Left reason -> error reason
        Right vs -> undefined

fact3 :: Int -> Integer
fact3 = (map fact' [0..] !!)
  where
    fact' 0 = 1
    fact' n = fromIntegral n * fact' (n-1)

fact3 = (!!) fact3'
   where
       fact3' = map fact' l
       l = [0..]
       fact' 0 = 1
       fact' n = ...

whereで定義しているローカル関数fibはfib_memにぶら下がっているのに対してfib_mem_argの方はfib_mem_arg nに対してローカル関数fibがぶらさがっている．