average.js

function average(){
   numbers=average.arguments;
   sum=0;
   for(var i=0; i<numbers.length; i++){
      sum+=numbers[i]
   };
   return sum/numbers.length;
}

average.lisp

(defun average (&rest numbers)
  (/ (apply #'+ numbers)(length numbers)))

average.py

def average(*numbers):
   return float(sum(numbers))/len(numbers)