Add types to output table when printing dataframe

Author: mchav

src/Data/DataFrame/Internal.hs

@@ -105,6 +105,10 @@ instance Show DataFrame where
 asText :: DataFrame -> T.Text
 asText d =
   let header = "index" : map fst (sortBy (compare `on` snd) $ M.toList (columnIndices d))
+      types = V.toList $ V.filter (/= "") $ V.map getType (columns d)
+      getType Nothing = ""
+      getType (Just (BoxedColumn (column :: Vector a))) = T.pack $ show (Type.Reflection.typeRep @a)
+      getType (Just (UnboxedColumn (column :: VU.Vector a))) = T.pack $ show (Type.Reflection.typeRep @a)
       -- Separate out cases dynamically so we don't end up making round trip string
       -- copies.
       get (Just (BoxedColumn (column :: Vector a))) =
@@ -123,7 +127,7 @@ asText d =
       rows =
         transpose $
           zipWith (curry (V.toList . getTextColumnFromFrame d)) [0..] header
-   in showTable header rows
+   in showTable header ("Int":types) rows
 
 metadata :: DataFrame -> String
 metadata df = show (columnIndices df) ++ "\n" ++

src/Data/DataFrame/Util.hs

@@ -63,13 +63,14 @@ right = fillRight ' '
 center :: Int -> T.Text -> T.Text
 center = fillCenter ' '
 
-showTable :: [T.Text] -> [[T.Text]] -> T.Text
-showTable header rows =
+showTable :: [T.Text] -> [T.Text] -> [[T.Text]] -> T.Text
+showTable header types rows =
   let cs = map (\h -> ColDesc center h left) header
-      widths = [maximum $ map T.length col | col <- transpose $ header : rows]
+      widths = [maximum $ map T.length col | col <- transpose $ header : types : rows]
+      border = T.intercalate "---" [T.replicate width (T.singleton '-') | width <- widths]
       separator = T.intercalate "-|-" [T.replicate width (T.singleton '-') | width <- widths]
       fillCols fill cols = T.intercalate " | " [fill c width col | (c, width, col) <- zip3 cs widths cols]
-   in T.unlines $ fillCols colTitleFill header : separator : map (fillCols colValueFill) rows
+   in T.unlines $ border : fillCols colTitleFill header : separator : fillCols colTitleFill types : separator : map (fillCols colValueFill) rows
 
 headOr :: a -> [a] -> a
 headOr v [] = v