This is the artifact for the pearl paper “On Julia’s efficient algorithm for subtyping union types and covariant tuples.” It consists of two primary components:

  • An implementation of the subtyping algorithm running in a webpage. This implementation is modified only slightly from the one described in the paper to enable visualization.
  • The Coq source code for the proofs referenced in our paper.

Note that the artifact’s website ( runs a component of the artifact (the implementation of the algorithm) in the browser.