Fix bug in subdivideCurve.

1 files changed, 4 insertions, 2 deletions

diff --git a/Bezier.hs b/Bezier.hs
index ed464d8..941ad5b 100644
--- a/Bezier.hs
+++ b/Bezier.hs
@@ -19,6 +19,7 @@ data Polygonization = Polygonization
     , curveStartIndex   :: Int
     , curveSegmentCount :: Int
     }
+ deriving Show
 
 type AllocatedRange = Polygonization
 
@@ -37,12 +38,13 @@ xz :: Vector Float -> (Float,Float)
 xz v = (v!0, v!2)
 
 subdivideCurve :: Monad m => Float -> Curve -> AllocatedRange -> StorePoint m -> m Polygonization
+subdivideCurve δ curve range store | curveSegmentCount range < 2 = return range { curveSegmentCount = 0 }
 subdivideCurve δ curve range store = do
     let ts = sort $ take (curveSegmentCount range - 2) $ sampleCurve δ curve
-    n <- (\f -> foldr f (return 0) (zip [0..] (0 : ts))) $ \(i,t) _ -> do
+    n <- (\f -> foldr f return (zip [0..] (0 : ts)) 0) $ \(i,t) ret _ -> do
         let v = bezierEval curve t
         store (curveBufferID range) (curveStartIndex range + i) v
-        return i
+        ret i
     let v = bezierEval curve 1.0
     store (curveBufferID range) (curveStartIndex range + n + 1) v
     return range { curveSegmentCount = n + 2 }