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.




$ sml
Standard ML of New Jersey v110.67 [built: Fri Jul  4 09:00:58 2008]
- fun f (s1, s2, sep) = String.concatWith sep [s1, "", s2];
[autoloading]
[library $SMLNJ-BASIS/basis.cm is stable]
[autoloading done]
val f = fn : string * string * string -> string
- f ("Rosetta", "Code", ":");
val it = "Rosetta::Code" : string
-