The wedge product mentioned in that pseudocode is between two 2D vectors. Calling them U and V, this wedge product gives the following numerical quantity (which is technically a pseudoscalar or antiscalar, but it doesn't matter):

U ∧ V = U.x * V.y - U.y * V.x

I have a Grassmann algebra talk that provides an introduction to the wedge product:

http://www.terathon.com/gdc14_lengyel.pdf