Add function concat to concatenate Doc value

Author: tarleb

src/Foreign/Lua/Module/DocLayout.hs

@@ -48,13 +48,16 @@ module Foreign.Lua.Module.DocLayout (
 
   -- * Functions
   , render
+  , concat
 
   -- * Marshaling
   , peekDoc
   , pushDoc
   )
 where
 
+import Prelude hiding (concat)
+import Data.List (intersperse)
 import Data.Text (Text)
 import Foreign.Lua (Lua, NumResults (..), Optional,
                     Peekable, Pushable, StackIndex)
@@ -101,6 +104,7 @@ pushModule = do
   Lua.addfunction "rblock"     rblock
   Lua.addfunction "vfill"      vfill
   -- renderign
+  Lua.addfunction "concat" concat
   Lua.addfunction "render" render
   return 1
 
@@ -115,6 +119,13 @@ preloadModule = flip Lua.preloadhs pushModule
 render :: Doc Text -> Optional Int -> Lua Text
 render doc optLength = return $ Doc.render (Lua.fromOptional optLength) doc
 
+-- | Concatenates a list of @'Doc'@s.
+concat :: [Doc Text] -> Optional (Doc Text) -> Lua (Doc Text)
+concat docs optSep = return $
+  case Lua.fromOptional optSep of
+    Nothing  -> mconcat docs
+    Just sep -> mconcat $ intersperse sep docs
+
 --
 -- Constructors
 --

test/test-doclayout.lua

@@ -30,6 +30,28 @@ return {
       test('empty doc', function ()
         assert.are_equal(doclayout.render(doclayout.empty), '')
       end)
+    },
+
+    group 'concat' {
+      test('without sep', function ()
+        local list = {
+          doclayout.literal 'one',
+          doclayout.literal 'two',
+          doclayout.literal 'three'
+        }
+        local sep = doclayout.cr
+        assert.are_equal(
+          doclayout.concat(list, sep),
+          list[1] .. sep .. list[2] .. sep .. list[3])
+      end),
+      test('without sep', function ()
+        local list = {
+          doclayout.literal 'one',
+          doclayout.literal 'two',
+          doclayout.literal 'three'
+        }
+        assert.are_equal(doclayout.concat(list), list[1] .. list[2] .. list[3])
+      end),
     }
   },