number printing for Skippy

gistfile1.lisp

(defun gif-write-integer (n image index x y)
  (let ((digits #(#*111101101101111
                  #*001011101001001
                  #*111001111100111
                  #*111001111001111
                  #*101101111001001
                  #*111100111001111
                  #*111100111101111
                  #*111001010010100
                  #*111101111101111
                  #*111101111001111)))
    (flet ((write-digit (n x y)
             (loop for b across (elt digits n)
                for i from 0
                if (= b 1) do  (setf (pixel-ref image (+ x (mod i 3)) (+ y (floor i 3))) index))))
      (cond
        ((< n 0) (error "Number must be positive"))
        ((= n 0) (write-digit 0 x y))
        (t (loop with nstr = (princ-to-string n)
                and curx = x
                for digit in (map 'list #'digit-char-p nstr)
                do (write-digit digit curx y) (incf curx 4)))))))