Use tasty for tests, fix bug in circOnLine

src/Geometry/Intersect.hs

@@ -77,6 +77,7 @@ intersectSegLine (V2 x1 y1) (V2 x2 y2) (V2 x3 y3) (V2 x4 y4)
     --u'  = (y1-y2)*(x1-x3) - (x1-x2)*(y1-y3)
 -- | It is not always necessary to find a point of intersection, sometimes a
 -- test may suffice.
+-- IS THIS CORRECT? -- TODO tests
 intersectSegSegTest
     :: Point2
     -> Point2
@@ -84,11 +85,11 @@ intersectSegSegTest
     -> Point2
     -> Bool
 {-# INLINE intersectSegSegTest #-}
-intersectSegSegTest a' b' c' d' 
-    = f a' b' c' d' && f c' d' a' b'
+intersectSegSegTest x y z w
+    = f x y z w && f z w x y
   where
-    f a b c d =  (      isLHS a b c  && not (isLHS a b d) ) 
-              || ( not (isLHS a b c) &&      isLHS a b d  )
+    f a b c d =  ( not (isRHS a b c) && not (isLHS a b d) ) 
+              || ( not (isLHS a b c) && not (isRHS a b d) )
 intersectSegSegPreTest
     :: Point2
     -> Point2

src/Geometry/LHS.hs

@@ -3,7 +3,7 @@ module Geometry.LHS
     , isRHS
     ) where
 import Geometry.Data
--- | Test whether a point is on the LHS of a line.
+-- | Test whether a point is stricly on the LHS of a line.
 -- Returns False if the line is of zero length.
 isLHS 
     :: Point2  -- ^ First line point.