Allow setting a doc below another via "devision"

Author: tarleb

src/Foreign/Lua/Module/DocLayout.hs

@@ -58,7 +58,7 @@ where
 import Data.Text (Text)
 import Foreign.Lua (Lua, NumResults (..), Optional,
                     Peekable, Pushable, StackIndex)
-import Text.DocLayout ((<+>), Doc)
+import Text.DocLayout (Doc, (<+>), ($$))
 
 import qualified Data.Text as T
 import qualified Foreign.Lua as Lua
@@ -251,6 +251,7 @@ pushDoc = Lua.pushAnyWithMetatable pushDocMT
     pushDocMT = Lua.ensureUserdataMetatable docTypeName $ do
       Lua.addfunction "__add"      __add
       Lua.addfunction "__concat"   __concat
+      Lua.addfunction "__div"      __div
       Lua.addfunction "__eq"       __eq
       Lua.addfunction "__tostring" __tostring
 
@@ -265,6 +266,10 @@ __add a b = return (a <+> b)
 __concat :: Doc Text -> Doc Text -> Lua (Doc Text)
 __concat a b = return (a <> b)
 
+-- | @a / b@ puts @a@ above @b@.
+__div :: Doc Text -> Doc Text -> Lua (Doc Text)
+__div a b = return (a $$ b)
+
 -- | Test @'Doc'@ equality.
 __eq :: Doc Text -> Doc Text -> Lua Bool
 __eq a b = return (a == b)

test/test-doclayout.lua

@@ -55,10 +55,16 @@ return {
     end),
 
     test('adding concatenates with space', function ()
-      local helloworld = doclayout.literal "Hello,"
+      local helloworld = doclayout.literal 'Hello,'
         .. doclayout.space
-        .. doclayout.literal "World"
+        .. doclayout.literal 'World'
       assert.are_equal(doclayout.literal 'Hello,' + 'World', helloworld)
-    end)
+    end),
+
+    test('dividing sets the first above the second', function ()
+      local first = doclayout.literal 'first'
+      local second = doclayout.literal 'second'
+      assert.are_equal(first / second, first .. doclayout.cr .. second)
+    end),
   }
 }