From a5647e17247232f8cb05379ce046142248810f31 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Wed, 11 Feb 2015 20:51:34 -0500
Subject: Fragment: Give up and use pattern matching
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

I’m normally opposed to pattern matching in high-quality apps, but this
is so small that I’m unconvinced it’ll be a problem.  I can always
switch to explicit accessors if things get too coupled.
---
 src/Tangle.hs | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

(limited to 'src/Tangle.hs')

diff --git a/src/Tangle.hs b/src/Tangle.hs
index 049c497..edfd6ed 100644
--- a/src/Tangle.hs
+++ b/src/Tangle.hs
@@ -12,6 +12,7 @@ PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 You should have received a copy of the GNU General Public License along with
 this program.  If not, see <http://www.gnu.org/licenses/>. -}
 
+{-# LANGUAGE RecordWildCards #-}
 module Tangle (tangle) where
 
 import Control.Exception (assert)
@@ -19,8 +20,7 @@ import Control.Monad (liftM)
 import Data.Map.Strict (Map)
 import qualified Data.Map.Strict as Map
 
-import Fragment (Fragment, isBlockCode, blockName, blockContents,
-                 CodeOrReference(Code, Reference))
+import Fragment (Fragment(..), CodeOrReference(..))
 
 type FragmentGraph = Map String [CodeOrReference]
 
@@ -28,24 +28,32 @@ tangle :: [Fragment] -> Either String String
 tangle fragments =
   case filter isBlockCode fragments of
     [] -> Right ""
-    codeBlocks@(root:_) ->
-      expandBlock (fragmentGraph codeBlocks) (blockName root)
+    blockCodeFragments@((BlockCode rootName _):_) ->
+      expandBlockCodeFragment (fragmentGraph blockCodeFragments) rootName
+    (Documentation {..}):_ -> error "isBlockCode did not work correctly"
 
 fragmentGraph :: [Fragment] -> FragmentGraph
-fragmentGraph frags =
-  Map.fromListWith (++) $
-    map (\block -> blockToPair $ assert (isBlockCode block) block) frags
-  where blockToPair frag = (blockName frag, blockContents frag)
-
-expandBlock :: FragmentGraph -> String -> Either String String
-expandBlock fragments name =
+fragmentGraph =
+  Map.fromListWith (++) .
+    map (\block -> blockToPair $ assert (isBlockCode block) block)
+  where blockToPair (BlockCode name body) = (name, body)
+        blockToPair (Documentation {..}) =
+          error "Documentation fragments cannot be converted to pairs"
+
+expandBlockCodeFragment :: FragmentGraph -> String -> Either String String
+expandBlockCodeFragment fragments name =
   case Map.lookup name fragments of
     Nothing -> Left $ "Desired node " ++ name ++ " not in fragment graph"
-    Just block -> concatMapM (expandBlockBody1 fragments) block
+    Just block -> concatMapM (expandBlockCodeBody fragments) block
+
+expandBlockCodeBody :: FragmentGraph -> CodeOrReference -> Either String String
+expandBlockCodeBody _ (Code body) = Right body
+expandBlockCodeBody fragments (Reference name) =
+  expandBlockCodeFragment fragments name
 
-expandBlockBody1 :: FragmentGraph -> CodeOrReference -> Either String String
-expandBlockBody1 _ (Code body) = Right body
-expandBlockBody1 fragments (Reference name) = expandBlock fragments name
+isBlockCode :: Fragment -> Bool
+isBlockCode (Documentation {..}) = False
+isBlockCode (BlockCode {..}) = True
 
 concatMapM :: Monad m => (a -> m [b]) -> [a] -> m [b]
 concatMapM f lists = liftM concat $ mapM f lists
-- 
cgit v1.2.3