Many language implementations come with an interactive mode.

This is a command-line interpreter that reads lines from the user and evaluates these lines as statements or expressions.

An interactive mode may also be known as a command mode,   a read-eval-print loop (REPL),   or a shell.



Task

Show how to start this mode.

Then, as a small example of its use, interactively create a function of two strings and a separator that returns the strings separated by two concatenated instances of the separator   (the 3rd argument).



Example

             f('Rosetta',  'Code',  ':')   

should return

             'Rosetta::Code'               



Note

This task is   not   about creating your own interactive mode.




 
;; screen copy of the REPL
;; note that the &i variables remember expression evaluation, and may be used in other expressions
 
EchoLisp - 2.16.2
📗 local-db: db.version: 3
(define ( f s1 s2 s3) (string-append s1 s3 s3 s2))
[0]→ f
(f "Rosetta" "Code" ":")
[1]→ "Rosetta::Code"
(+ 4 8)
[2]→ 12
(* 4 8)
[3]→ 32
(* &2 &3)
[4]→ 384
(f &1 &1 ":")
[5]→ "Rosetta::Code::Rosetta::Code"
 
;; etc.
 