Merge pull request #12 from Cambridge-ICCS/impl2

Implement `equation_of_line` using determinant approach

maths.py

@@ -9,17 +9,7 @@ def equation_of_line(a, b):
     x0, y0 = a
     x1, y1 = b
 
-    if (x0 == x1):
-        # Special case of a vertical line
-
-        def f(x, y):
-            return x - x0
-
-    else:
-
-        def f(x, y):
-            m = (y1 - y0) / (x1 - x0)
-            c = y0 - m * x0
-            return y - m * x - c
+    def f(x, y):
+        return (x1 - x0) * (y - y0) - (y1 - y0) * (x - x0)
 
     return f