CommonLisp "rows" done for a task @ prooops #coders

rows.lisp

; Simple print-rows for prooops #coders
; Print * (+1 for every row) and in the middle print as may stars as there are rows. (rows marks the middle)
#|
Example:
rows = 5
*
**
***
****
********* (9*)
****
***
**
*
|#

; Easiest way without loop:
(defparameter *rows* 0)

; 1) Write function, which only prints as many * as you wish (returns #\newline at the end)
(defun aster (cur num)
  (if (> num cur)
    (progn
      (princ #\*)
      (aster (1+ cur) num))
    (princ #\Newline)))

; 2) Write function, which knows in which row we are and how many we need.

(defun linenumber (row)
  (if (> *rows* row)
    (progn
      (aster 0 row)
      (linenumber (1+ row))
      ))
  (if (= *rows* row)
    (progn
      (aster 0 (1+ (* 2 (1- *rows*))))
      (linenumber (1+ row))
      ))
  (if (< *rows* row)
    (if (<= row (1+ (* 2 (1- *rows*))))
      (progn
        (aster 0 (- *rows* (- row *rows*)))
        (linenumber (1+ row))
        )
      (print_rows)
      )
    )
  )
    
(defun print_rows ()
  (format t "~% How many rows?~%")
  (setf *rows* (parse-integer (read-line) :junk-allowed t))
  (format t "rows:~a" *rows*)
  (linenumber 0)
  )    
    
(print_rows)