miniblog.

On how far programming language research has come, and the maturity of tools and techniques that make more ambitious projects viable:

Common Lisp has a function change-class that lets you change the class of instance (like reassigning __class__ in Python). http://clhs.lisp.se/Body/f_chg_cl.htm I love the note at the end: "semantic difficulties" if you call any methods whilst the class changes!

Beyond structural editing: semantic editing! https://reasonablypolymorphic.com/blog/towards-tactics/index.html (Uses Coq-style tactics.)