diff --git a/src/DividedRectangles.jl b/src/DividedRectangles.jl
index e012b88..1f289b5 100644
--- a/src/DividedRectangles.jl
+++ b/src/DividedRectangles.jl
@@ -19,6 +19,11 @@ function is_ccw(a::DirectRectangle, b::DirectRectangle, c::DirectRectangle)
     return a.r*(b.y-c.y)-a.y*(b.r-c.r)+(b.r*c.y-b.y*c.r) < 1e-6
 end
 
+"""
+A helper function that returns a basis vector with a single 1 entry in an otherwise zero vector.
+"""
+basis(i, n) = [k == i ? 1.0 : 0.0 for k in 1 : n]
+
 """
 A routine for obtaining the split intervals from a given list of intervals and a minimum radius.
 The potentially optimal intervals form a lower-right convex hull in r and y.