    {-# LANGUAGE CPP #-}
    #if __GLASGOW_HASKELL__ >= 701
    {-# LANGUAGE Safe #-}
    #endif

    -- | Table combinators for XHTML.
    module Text.XHtml.Table (HtmlTable, HTMLTABLE(..),
                            (</>), above, (<->), beside,
                             aboves, besides,
                             simpleTable) where

    import Text.XHtml.Internals
    import Text.XHtml.Strict.Elements
    import Text.XHtml.Strict.Attributes

    import qualified Text.XHtml.BlockTable as BT

    infixr 3 </>  -- combining table cells
    infixr 4 <->  -- combining table cells

    --
    -- * Tables
    --

    class HTMLTABLE ht where
          cell :: ht -> HtmlTable

    instance HTMLTABLE HtmlTable where
          cell = id

    instance HTMLTABLE Html where
          cell h =
             let
                  cellFn x y = h ! (add x colspan $ add y rowspan $ [])
                  add 1 _  rest = rest
                  add n fn rest = fn n : rest
                  r = BT.single cellFn
             in
                  mkHtmlTable r

    -- | We internally represent the Cell inside a Table with an
    -- object of the type
    --
    -- >	   Int -> Int -> Html
    --
    -- When we render it later, we find out how many columns
    -- or rows this cell will span over, and can
    -- include the correct colspan\/rowspan command.
    newtype HtmlTable
          = HtmlTable (BT.BlockTable (Int -> Int -> Html))

    mkHtmlTable :: BT.BlockTable (Int -> Int -> Html) -> HtmlTable
    mkHtmlTable r = HtmlTable r

    -- We give both infix and nonfix, take your pick.
    -- Notice that there is no concept of a row/column
    -- of zero items.

    (</>),above,(<->),beside :: (HTMLTABLE ht1,HTMLTABLE ht2)
                           => ht1 -> ht2 -> HtmlTable
    above   a b = combine BT.above (cell a) (cell b)
    (</>)         = above
    beside  a b = combine BT.beside (cell a) (cell b)
    (<->) = beside

    combine :: (BT.BlockTable (Int -> Int -> Html) ->
                BT.BlockTable (Int -> Int -> Html) ->
                BT.BlockTable (Int -> Int -> Html))
            -> HtmlTable
            -> HtmlTable
            -> HtmlTable
    combine fn (HtmlTable a) (HtmlTable b) = mkHtmlTable (a `fn` b)

    -- Both aboves and besides presume a non-empty list.
    -- here is no concept of a empty row or column in these
    -- table combinators.

    aboves :: (HTMLTABLE ht) => [ht] -> HtmlTable
    aboves []  = error "aboves []"
    aboves xs  = foldr1 (</>) (map cell xs)

    besides :: (HTMLTABLE ht) => [ht] -> HtmlTable
    besides [] = error "besides []"
    besides xs = foldr1 (<->) (map cell xs)

    -- | renderTable takes the HtmlTable, and renders it back into
    --   and Html object.
    renderTable :: BT.BlockTable (Int -> Int -> Html) -> Html
    renderTable theTable
          = concatHtml
              [tr << [theCell x y | (theCell,(x,y)) <- theRow ]
                          | theRow <- BT.getMatrix theTable]

    instance HTML HtmlTable where
          toHtml (HtmlTable tab) = renderTable tab

    instance Show HtmlTable where
          showsPrec _ (HtmlTable tab) = shows (renderTable tab)

    -- | If you can't be bothered with the above, then you
    -- can build simple tables with simpleTable.
    -- Just provide the attributes for the whole table,
    -- attributes for the cells (same for every cell),
    -- and a list of lists of cell contents,
    -- and this function will build the table for you.
    -- It does presume that all the lists are non-empty,
    -- and there is at least one list.
    --
    -- Different length lists means that the last cell
    -- gets padded. If you want more power, then
    -- use the system above, or build tables explicitly.
    simpleTable :: [HtmlAttr] -> [HtmlAttr] -> [[Html]] -> Html
    simpleTable attr cellAttr lst
          = table ! attr
              <<  (aboves
                  . map (besides . map ((td ! cellAttr) . toHtml))
                  ) lst