Task

Given a prompt and a list containing a number of strings of which one is to be selected, create a function that:

 prints a textual menu formatted as an index value followed by its corresponding string for each item in the list;
 prompts the user to enter a number;
 returns the string corresponding to the selected index number.


The function should reject input that is not an integer or is out of range by redisplaying the whole menu before asking again for a number. The function should return an empty string if called with an empty list.

For test purposes use the following four phrases in a list:

   fee fie
   huff and puff
   mirror mirror
   tick tock

Note

This task is fashioned after the action of the Bash select statement.

showmenu <- function(choices = NULL)
{
   if (is.null(choices)) return("")
   ans <- menu(choices)
   if(ans==0) "" else choices[ans]
 
}
str <- showmenu(c("fee fie", "huff and puff", "mirror mirror", "tick tock"))
str <- showmenu()
 