+(defun position-char (char string start max)
+ "From KMRCL."
+ (declare (optimize (speed 3) (safety 0) (space 0))
+ (fixnum start max) (simple-string string))
+ (do* ((i start (1+ i)))
+ ((= i max) nil)
+ (declare (fixnum i))
+ (when (char= char (schar string i)) (return i))))
+