title: lisp (scheme) function that works with and without an argument
body: <p>I'm working on an assignment where I have to construct a function which takes a single argument and returns various things. However, it is also supposed to do something when it is evaluated without an argument and I don't know how to do this. Does anyone know how one would go about implementing such a function? Could I perhaps set a condition that if it is evaluated with an argument it does x and if there is no argument it does y?</p>