Some major changes for expressions. (#33)

* Add interpreter for expression language.
* Remove copius reflection and use type families.
* Change some examples to use the new derive API
* deprecate deriveFrom

Author: mchav

app/Main.hs

@@ -101,8 +101,7 @@ chipotle = do
   print $ D.take 10 f
 
   -- Create a total_price column that is quantity * item_price
-  let multiply (a :: Int) (b :: Double) = fromIntegral a * b
-  let withTotalPrice = D.deriveFrom (["quantity", "item_price"], D.func multiply) "total_price" f
+  let withTotalPrice = D.derive "total_price" (D.lift fromIntegral (D.col @Int "quantity") * D.col @Double"item_price") f
 
   -- sample a filtered subset of the dataframe
   putStrLn "Sample dataframe"

dataframe.cabal

@@ -24,6 +24,7 @@ source-repository head
 library
     exposed-modules: DataFrame
     other-modules: DataFrame.Internal.Types,
+                   DataFrame.Internal.Expression,
                    DataFrame.Internal.Function,
                    DataFrame.Internal.Parsing,
                    DataFrame.Internal.Column,
@@ -60,6 +61,7 @@ executable dataframe
     main-is:       Main.hs
     other-modules: DataFrame,
                    DataFrame.Internal.Types,
+                   DataFrame.Internal.Expression,
                    DataFrame.Internal.Function,
                    DataFrame.Internal.Parsing,
                    DataFrame.Internal.Column,

docs/coming_from_dplyr.md

@@ -111,7 +111,7 @@ starwars
   |> D.selectRange ("name", "mass")
   -- mass and height are optionals so we combine them with
   -- Haskell's Applicative operators.
-  |> D.deriveFrom (["mass", "height"], D.func (\w h -> bmi <$> w <*> h)) "bmi" 
+  |> D.derive "bmi" (lift2 (/) (lift fromIntegral (col @Int "mass")) (lift fromIntegral (col@ Int "height")))
   |> D.take 10
 ```
 

src/DataFrame.hs

@@ -5,6 +5,7 @@ module DataFrame
 where
 
 import DataFrame.Internal.Types as D
+import DataFrame.Internal.Expression as D
 import DataFrame.Internal.Function as D
 import DataFrame.Internal.Parsing as D
 import DataFrame.Internal.Column as D

src/DataFrame/Display/Terminal/Plot.hs

@@ -5,6 +5,7 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE TupleSections #-}
+{-# LANGUAGE FlexibleContexts #-}
 module DataFrame.Display.Terminal.Plot where
 
 import qualified Data.List as L
@@ -19,9 +20,8 @@ import Control.Monad ( forM_, forM )
 import Data.Bifunctor ( first )
 import Data.Char ( ord, chr )
 import DataFrame.Display.Terminal.Colours
-import DataFrame.Internal.Column (Column(..))
+import DataFrame.Internal.Column (Column(..), Columnable)
 import DataFrame.Internal.DataFrame (DataFrame(..))
-import DataFrame.Internal.Types (Columnable)
 import DataFrame.Operations.Core
 import Data.Maybe (fromMaybe)
 import Data.Typeable (Typeable)

src/DataFrame/Errors.hs

@@ -22,8 +22,8 @@ data DataFrameException where
                           -> T.Text    -- ^ call point
                           -> DataFrameException
     TypeMismatchException' :: forall a . (Typeable a)
-                           => TypeRep a -- ^ expected type
-                           -> String    -- ^ given type
+                           => TypeRep a -- ^ given type
+                           -> String    -- ^ expected type
                            -> T.Text    -- ^ column name
                            -> T.Text    -- ^ call point
                            -> DataFrameException