(defun range (a b &optional c)
  "Builds a range of numbers as Fortran and Matlab would do"
  (flet ((|:| (start step stop)
           (assert (and (<= start stop) (> step 0)))
           (loop for x from start to stop by step collect x)))
    (if c
        (|:| a b c)
        (|:| a 1 b))))