1 files changed, 33 insertions, 0 deletions
diff --git a/Graphics/Glyph/ArrayGenerator.hs b/Graphics/Glyph/ArrayGenerator.hs
new file mode 100644
index 0000000..1e9e5a3
--- /dev/null
+++ b/Graphics/Glyph/ArrayGenerator.hs
@@ -0,0 +1,33 @@
+{-# LANGUAGE UndecidableInstances #-}
+module Graphics.Glyph.ArrayGenerator where
+
+import qualified Data.Map as M
+
+import Data.Array
+import Data.Maybe
+
+data ArrayTransaction ix val b = ArrayBuilderM_ (M.Map ix val) b
+instance (Ord ix) => Monad (ArrayTransaction ix a) where
+    return = ArrayBuilderM_ M.empty
+    (ArrayBuilderM_ map1 val) >>= f = 
+        ArrayBuilderM_ (map1 `M.union` map2) val2
+        where (ArrayBuilderM_ map2 val2) = f val
+
+class HasDefault a where
+    theDefault :: a
+
+instance (Num a) => HasDefault a where
+    theDefault = 0
+instance (HasDefault a, HasDefault b) => HasDefault (a,b) where
+    theDefault = (theDefault,theDefault)
+instance (HasDefault a, HasDefault b, HasDefault c) => HasDefault (a,b,c) where
+    theDefault = (theDefault,theDefault,theDefault)
+
+writeArray :: ix -> a -> ArrayTransaction ix a ()
+writeArray index' val = ArrayBuilderM_ (M.singleton index' val) ()
+
+buildArray :: (Ix ix) => (ix,ix) -> e -> ArrayTransaction ix e () -> Array ix e
+buildArray bounds' def (ArrayBuilderM_ map' _) =
+    listArray bounds' [maybeLookup map' bound | bound <- range bounds'] 
+    where maybeLookup map_ key = fromMaybe def (M.lookup key map_)
+