Implement Arbitrary for Vertex

genstar/Main.hs

@@ -1,6 +1,7 @@
 module Main where
 
 import Control.Monad (join)
+import Test.QuickCheck (Arbitrary (arbitrary))
 
 -- | One point of a path, consisting of its \(x\) and \(y\) coordinates.
 newtype Vertex = Point (Double, Double)
@@ -8,6 +9,12 @@ newtype Vertex = Point (Double, Double)
 instance Show Vertex where
   show (Point (x, y)) = show x ++ " " ++ show y
 
+instance Arbitrary Vertex where
+  arbitrary = do
+    x <- arbitrary
+    y <- arbitrary
+    return (Point (x, y))
+
 -- | 'fromAngle' @angle@
 -- creats a point on the unit circle at the specified angle
 -- (specified in radians).