"...I'm sure there's a dozen more languages that allow you to redefine at runtime"
Indeed. There are all the Lisp dialects to start with.
And it's no surprise that hence SmallTalk had this feature too: Alan Kay (+), one of the key creator of SmallTalk, acknowledged the heavy influence of Lisp on SmallTalk:
This exactly. Tim Berners Lee and Roy Fielding both conceived of the web as a giant Lisp machine oriented around the URL / Hypermedia concept. HTML and the subsequent XML is a crippled form of an s-expression. If you change the tags into parens, map the functions into visual structure, you have a Lisp. TBL's first web browser in 1991 was a two-way client: you could edit the page and submit it back to the server and it would publish it. ReST is how distributed computing was meant to work in a homoiconic language. And JSON? C'mon, change the colon, bang, it's a Lisp. Lisp is fundamental; the AST is the avatar of all languages.
Indeed. There are all the Lisp dialects to start with.
And it's no surprise that hence SmallTalk had this feature too: Alan Kay (+), one of the key creator of SmallTalk, acknowledged the heavy influence of Lisp on SmallTalk:
http://www.franz.com/services/conferences_seminars/lisp_50th...
(+) Famous quote attributed to Alan Kay: "I coined the term "object oriented". I can tell you I didn't have C++ in mind."