Demo of session immutatibility in clara-rules

repl_session.clj

clara.test-rules> (com/clear-session-cache!)
{}
clara.test-rules> (defrule first->second-rule
                    [First]
                    =>
                    (insert! (->Second)))
#'clara.test-rules/first->second-rule
clara.test-rules> (defquery second-query
                    []
                    [Second])
#'clara.test-rules/second-query
clara.test-rules> (def empty-session (mk-session [first->second-rule second-query]))
#'clara.test-rules/empty-session
clara.test-rules> (-> empty-session
                      (insert (->First))
                      fire-rules
                      (query second-query))
({})
clara.test-rules> (query empty-session second-query)
()
clara.test-rules> (type (insert empty-session (->First)))
clara.rules.engine.LocalSession
clara.test-rules>