eintr: optional Exercise

 
 5.5 ‘optional’ Argument Exercise
 ================================
 
 Write an interactive function with an optional argument that tests
 whether its argument, a number, is greater than or equal to, or else,
 less than the value of ‘fill-column’, and tells you which, in a message.
 However, if you do not pass an argument to the function, use 56 as a
 default value.