How can I avoid the nil printed in the end?

Question

I have coded this function that prints-out the state of the board, but in the end, due to the fact that there isnt no return the function prints an nil!

Function:

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Answer 1

You can get rid of multiple formats in the code:

Usually in a functional language I would return a value. It makes sense to return the board itself. Since such a function is usually called from game logic, a return value may be useful and it does not matter for output then.

(defun show-board (board)
  (dotimes (i 8)
    (dotimes (j 8)
      (write-string (case (aref board i j)
                      (0         "B ")
                      (1         "P ")
                      (otherwise "L "))))
    (terpri))
  board)