Robert Smith gave a nice presentation involving using the MOP for defining abstract, final and singleton classes. Then he goes down a rabbit hole of user-defined JIT compilation:<p><a href="https:&#x2F;&#x2F;dl.dropboxusercontent.com&#x2F;u&#x2F;734346&#x2F;JIT-Compilation-of-Symbolic-Functions_Robert-Smith.pdf" rel="nofollow">https:&#x2F;&#x2F;dl.dropboxusercontent.com&#x2F;u&#x2F;734346&#x2F;JIT-Compilation-o...</a>