(defun gnuplot (&rest coms)
 (let ((str  (with-output-to-string (s)
               (format s "~a<<EOF~%" (which "gnuplot"))
               (dolist (com coms)
                 (format s "~a~%" com))
               (format s "~a" "EOF")))
       (file   (tmp-file)))
   (with-open-file (s file :direction :output 
                           :if-exists :overwrite)
     (format s "~a~%" str))
   (prog1
       (sh "bash" file)
     (delete-file file))))

(defun demo-gnuplot1 () 
  (gnuplot "set terminal dumb" 
           "set size 0.75,1"
           "set xrange [-5:5]"
           "set yrange [-1.2:1.2]"
           "plot sin(x)"))

(defun demo-gnuplot2-mac-osx ()
  (let* ((file (format nil "~a/plot.png" (tmp-dir))))
    (gnuplot "set terminal pdf" 
             (format nil "set output '~a'~%" file) 
             "plot sin(x)")
    (sh "xpdf" file  "&")))

(deftest test-gnuplot ()
  (check
   (samep (demo-gnuplot1) "
      +----+---------+---------+---------+---------+----+
      |    +         +         +         +sin(x) ****** |
    1 *****                          *****             ++
      |   **                        *    **             |
      |    **                      *      **            |
      |     *                     *        *            |
  0.5 ++     *                   **         *          ++
      |       *                  *           *          |
      |       *                 *            *          |
      |        *                *             *         |
    0 ++       *               *               *       ++
      |         *             *                *        |
      |          *            *                 *       |
      |          *           *                  *       |
 -0.5 ++          *         **                   *     ++
      |            *        *                     *     |
      |            **      *                      **    |
      |             **    *                        **   |
   -1 ++             *****                          *****
      |    +         +         +         +         +    |
      +----+---------+---------+---------+---------+----+
          -4        -2         0         2         4")))