feat: make numeric column conversion functions more general.

Author: mchav

src/DataFrame/Operations/Core.hs

@@ -864,7 +864,8 @@ Returns 'Left' with a 'DataFrameException' if the column cannot be converted to
 This may occur if the column contains non-numeric data or values outside the 'Int' range.
 -}
 columnAsIntVector ::
-    Expr Int -> DataFrame -> Either DataFrameException (VU.Vector Int)
+    (Columnable a, Num a) =>
+    Expr a -> DataFrame -> Either DataFrameException (VU.Vector Int)
 columnAsIntVector (Col name) df = case getColumn name df of
     Just col -> toIntVector col
     Nothing ->
@@ -880,7 +881,8 @@ Returns 'Left' with a 'DataFrameException' if the column cannot be converted to
 This may occur if the column contains non-numeric data.
 -}
 columnAsDoubleVector ::
-    Expr Double -> DataFrame -> Either DataFrameException (VU.Vector Double)
+    (Columnable a, Num a) =>
+    Expr a -> DataFrame -> Either DataFrameException (VU.Vector Double)
 columnAsDoubleVector (Col name) df = case getColumn name df of
     Just col -> toDoubleVector col
     Nothing ->
@@ -896,7 +898,8 @@ Returns 'Left' with a 'DataFrameException' if the column cannot be converted to
 This may occur if the column contains non-numeric data.
 -}
 columnAsFloatVector ::
-    Expr Float -> DataFrame -> Either DataFrameException (VU.Vector Float)
+    (Columnable a, Num a) =>
+    Expr a -> DataFrame -> Either DataFrameException (VU.Vector Float)
 columnAsFloatVector (Col name) df = case getColumn name df of
     Just col -> toFloatVector col
     Nothing ->

src/DataFrame/Synthesis.hs

@@ -266,7 +266,9 @@ percentiles :: DataFrame -> [Expr Double]
 percentiles df =
     let
         doubleColumns =
-            map (either throw id . ((`columnAsDoubleVector` df) . Col)) (D.columnNames df)
+            map
+                (either throw id . ((`columnAsDoubleVector` df) . Col @Double))
+                (D.columnNames df)
      in
         concatMap
             (\c -> map (Lit . roundTo2SigDigits . (`percentile'` c)) [1, 25, 75, 99])