Add docstrings to math.py

geom/math.py

@@ -2,27 +2,64 @@ import math
 
 ZERO = (0, 0)
 
+
 def dot(x1, y1, x2, y2):
+    """Returns the dot product of two vectors."""
     return (x1 * x2) + (y1 * y2)
 
+
 def length(x, y):
+    """Returns the magnitude of a vector."""
     return math.sqrt((x * x) + (y * y))
 
 def normalize(x, y):
+    """Returns the unit vector pointed in the same direction as [x, y]."""
     _len = length(x, y)
     return x / _len, y / _len
 
+
+def lnormal(x, y):
+    """Returns the left-hand normal of a vector."""
+    return -y, x
+
+
+def rnormal(x, y):
+    """Returns the right-hand normal of a vector."""
+    return y, -x
+
+
+def reverse(x, y):
+    """Returns a vector pointing in the opposite direction."""
+    return -x, -y
+
+
 def scale(x, y, factor):
+    """Scale a vector by a given factor."""
     return x * factor, y * factor
 
+
 def add(x1, y1, x2, y2):
+    """Add two vectors."""
     return x1 + x2, y1 + y2
 
+
 def sub(x1, y1, x2, y2):
+    """Subtract a vector from another."""
     return x1 - x2, y1 - y2
 
+
 def vmin(x1, y1, x2, y2):
+    """Return the minimum [x, y] components of the given vectors."""
     return min(x1, x2), min(y1, y2)
 
+
 def vmax(x1, y1, x2, y2):
+    """Return the maximum [x, y] components of the given vectors."""
     return max(x1, x2), max(y1, y2)
+
+
+def is_equal(x1, y1, x2, y2):
+    """Returns true if two unit vectors are pointed in either the same or
+    opposite directions.
+    """
+    return math.isclose(abs(dot(x1, y1, x2, y2)), 1, rel_tol=1e-03)