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.





name: myapp
version: "1.0"
author: A Rust Developer <rustme@home.com>
about: Does awesome things
args:
  - STRING1:
      about: First string to use
      required: true
      index: 1
  - STRING2:
      about: Second string to use
      required: true
      index: 2
  - SEPARATOR:
      about: Separtor to use
      required: true
      index: 3
 