Fix the random number generation

src/lib.rs

@@ -152,10 +152,10 @@ impl<const N: usize> Plane<N> {
         source: &mut T,
     ) -> (Self, Vec<usize>, Vec<usize>) {
         debug_assert!(vectors.len() > 1);
-        let i = (indices.len() as f64 * source.read::<f64>()) as usize;
+        let i = source.read::<usize>() % indices.len();
         let mut j = i;
         while i == j {
-            j = (indices.len() as f64 * source.read::<f64>()) as usize;
+            j = source.read::<usize>() % indices.len();
         }
         let normal = vectors[j].subtract(&vectors[i]);
         let offset = -normal.product(&vectors[i].average(&vectors[j]));
@@ -220,8 +220,8 @@ mod tests {
         let vectors = vec![Vector([4.0, 2.0]), Vector([5.0, 7.0])];
         let indices = (0..vectors.len()).collect::<Vec<_>>();
         let (plane, above, below) = Plane::build(&vectors, &indices, &mut source);
-        assert::close(&plane.normal.0, &[1.0, 5.0], 1e-6);
-        assert_eq!(above, &[1]);
-        assert_eq!(below, &[0]);
+        assert::close(&plane.normal.0, &[-1.0, -5.0], 1e-6);
+        assert_eq!(above, &[0]);
+        assert_eq!(below, &[1]);
     }
 }