You can't change the way lookups happen at runtime in Lisps. In Ioke (and Io), you can modify the proto chain as the application runs. You can also add and re

You can't change the way lookups happen at runtime in Lisps. In Ioke (and Io), you can modify the proto chain as the application runs. You can also add and remove slots of objects. You can't add and remove variables from a closure in any Lisps that I am aware of.