implemented getRung

src/Abacus.hs

@@ -24,7 +24,15 @@ License along with this program.  If not, see
 
 -}
 
-module Abacus (Abacus, newAbacus, getNumBeads, getNumRungs) where
+module Abacus (
+  Abacus,
+  newAbacus,
+  getNumBeads,
+  getNumRungs,
+  getRung,
+  ) where
+
+import Data.List (find)
 
 import Abacus.Internal
 
@@ -48,4 +56,16 @@ getNumBeads = abacusNumBeads
 getNumRungs :: Abacus -> Int
 getNumRungs = length . abacusRungs
 
+-- | Returns the number of beads slid across a given rung
+getRung
+  :: Int
+  -- ^ The rung number
+  -> Abacus
+  -- ^ Abacus being checked
+  -> Maybe Int
+  -- ^ The number of beads slid across (if the rung exists)
+getRung r a = snd <$> find
+  (\(n, _) -> n == r)
+  (zip [0..] $ abacusRungs a)
+
 --jl