dynamic update

[Pradeep bhatt]

From chp1

Almost everything defined in a Clojure program can be re-defined, even while the
program is running: functions, multimethods, type hierarchies, even Java method
implementations as provided via proxy and gen-class.

Can someone help me understand the internal working ? Is it same as class reloading ?

[Hussein Baghdadi]

While I'm not sure and of course waiting for the authors to confirm but I think basically they are talking about Macros in Clojure and the Meta-programming capabilities.

[Chris Houser]

The exact mechanism used varies based on the kind of thing being reloaded.

Records and protocols (deftype, defrecord, and defprotocol) indeed do something like class reloading using a custom classloader provided by Clojure itself.

Most of the rest are built on top of Clojure Vars, which are a concurrency construct that allows for thread-safe mutation. Updating one of these amounts to making its Var point to the new definition.