There is indeed an FFI -- I played around a little bit with it a while ago.<p>&gt; you should consider using it only if you&#x27;re ready to do just that: heavily hack on its implementation.<p>That&#x27;s unfortunately another problem: the current Ur&#x2F;Web compiler, or at least when I last looked at it about 6 months ago, is tens of thousands of lines of SML, with almost <i>zero</i> comments or documentation. It&#x27;s truly one of the densest and most impenetrable code bases I&#x27;ve looked at. I have no idea how Adam Chlipala is able to grok it -- I guess he&#x27;s just that smart. Unfortunately, it makes outside contribution (especially from a person with limited experience with compilers, such as myself) nigh impossible. That, plus it&#x27;s not hosted on something like Github or Bitbucket, which would make it much easier to contribute to.