Work on selection sets

src/Dodge/SelectionSections.hs

@@ -8,6 +8,9 @@ module Dodge.SelectionSections (
     inverseSelSecYint,
     posSelSecYint,
     inverseSelNumPos,
+    ssLookupGE,
+    ssLookupLE,
+    sssSelectionSlice,
 ) where
 
 import Control.Applicative
@@ -149,6 +152,22 @@ ssLookupGT' i sss = do
         Just (j', si) -> return (i', j', si)
         Nothing -> ssLookupGT' i' sss
 
+ssLookupGE :: XInfinity (Int,Int) -> IMSS a -> Maybe (Int,Int,SelectionItem a)
+ssLookupGE x sss = case x of
+    NegInf -> ssLookupMin sss
+    PosInf -> Nothing
+    NonInf (i,j) -> case sss ^? ix i . ssItems . ix j of
+        Nothing -> ssLookupGT i j sss
+        Just s -> Just (i,j,s)
+
+ssLookupLE :: XInfinity (Int,Int) -> IMSS a -> Maybe (Int,Int,SelectionItem a)
+ssLookupLE x sss = case x of
+    NegInf -> Nothing
+    PosInf -> ssLookupMax sss
+    NonInf (i,j) -> case sss ^? ix i . ssItems . ix j of
+        Nothing -> ssLookupLT i j sss
+        Just s -> Just (i,j,s)
+
 ssLookupGE' :: Int -> IMSS a -> Maybe (Int, Int, SelectionItem a)
 ssLookupGE' i sss = do
     (i', ss) <- IM.lookupGE i sss
@@ -213,3 +232,14 @@ inverseSelSecYintXPosCheck cfig ldp x yint sss = do
 inverseSelNumPos :: Config -> LDParams -> Point2 -> IMSS a -> Maybe (XInfinity (Int, Int))
 inverseSelNumPos cfig ldp (V2 x y) =
     inverseSelSecYintXPosCheck cfig ldp x (posSelSecYint cfig ldp y)
+
+sssSelectionSlice :: IMSS a -> XInfinity (Int,Int) -> XInfinity (Int,Int) -> IMSS a
+sssSelectionSlice sss x1 x2 = fromMaybe mempty $ do
+    let (xmin,xmax) | x1 < x2 = (x1,x2)
+            | otherwise = (x2,x1)
+    (mini,minj,_) <- ssLookupGE xmin sss
+    (maxi,maxj,_) <- ssLookupLE xmax sss
+    return $ fst (IM.split (maxi+1) . snd $ IM.split (mini-1) sss)
+            & ix mini . ssItems %~ snd . IM.split (minj-1)
+            & ix maxi . ssItems %~ fst . IM.split (maxj+1)
+