One might think that a Listener is a particular user interface for a read-eval-print-loop. The REPL reads s-expressions, evaluates them and prints the resulting

One might think that a Listener is a particular user interface for a read-eval-print-loop. The REPL reads s-expressions, evaluates them and prints the resulting s-expresion(s). The Listener might be a window (or a terminal session), which allows typing, editing, commands, completion, help, etc. and which runs a REPL.