1 files changed, 63 insertions, 0 deletions

diff --git a/Mask.hs b/Mask.hs
new file mode 100644
index 0000000..0b91e42
--- /dev/null
+++ b/Mask.hs
@@ -0,0 +1,63 @@
+module Mask where
+
+import Data.Int
+
+newtype Mask = Mask [(Int32,Int32)]
+ deriving (Eq,Ord,Show)
+
+{-
+merge ((x0,x):xs) ((y0,y):ys) =
+    if x0 <= y0
+        then case compare x y0 of
+            LT -> (x0 x) (y0 y)
+            EQ -> (x0 x=y0 y)
+            GT -> if x <= y then -> (x0 y0 x y)
+                            else -> (x0 y0 y x)
+        else case compare x0 y of
+            LT -> if x <= y then (y0 x0 x y)
+                            else (y0 x0 y x)
+            EQ -> (y0 y=x0 x)
+            GT -> (y0 y) (x0 x)
+-}
+
+subtr [] ys = []
+subtr xs [] = xs
+subtr ((x0,x):xs) ((y0,y):ys) =
+    if x0 <= y0
+        then case compare x y0 of
+            LT -> subtr ((x0,x):xs) ys
+            EQ -> (x0,x) : subtr xs ((y0,y):ys)
+            GT -> if x <= y then (if x0<y0 then ((x0,y0) :) else id) $ subtr xs ((y0,y):ys)
+                            else (if x0<y0 then ((x0,y0) :) else id) $ subtr ((y,x):xs) ys
+        else case compare x0 y of
+            LT -> if x <= y then subtr xs ((y0,y):ys)
+                            else subtr ((y,x):xs) ys
+            EQ -> subtr ((x0,x):xs) ys
+            GT -> subtr ((x0,x):xs) ys
+
+union [] ys = ys
+union xs [] = xs
+union ((x0,x):xs) ((y0,y):ys) =
+    if x0 <= y0
+        then case compare x y0 of
+            LT -> (x0,x) : union xs ((y0,y):ys)
+            EQ -> (x0,y) : union xs ys
+            GT -> if x <= y then union xs ((x0,y):ys)
+                            else union ((x0,x):xs) ys
+        else case compare x0 y of
+            LT -> if x <= y then union xs ((y0,y):ys)
+                            else union ((y0,x):xs) ys
+            EQ -> (y0,x) : union xs ys
+            GT -> (y0,y) : union ((x0,x):xs) ys
+
+endpts :: (Int32,Int32) -> (Int32,Int32)
+endpts (x0,sz) = (x0,x0 + sz)
+
+sized :: (Int32,Int32) -> (Int32,Int32)
+sized (x0,x) = (x0, x - x0)
+
+maskPlus :: Mask -> Mask -> Mask
+maskPlus (Mask xs) (Mask ys) = Mask $ sized <$> union (endpts <$> xs) (endpts <$> ys)
+
+maskSubtract :: Mask -> Mask -> Mask
+maskSubtract (Mask xs) (Mask ys) = Mask $ sized <$> subtr (endpts <$> xs) (endpts <$> ys)