i'll add to general discussion about syntaxes and infix notation, i'm not sure where to attach this point to existing threads. genera had infix mode, that was enabled on a reader macro. you could write something like

    (defun bresenham (a x0 y0 x1 y1 &aux dx dy d y)
      #◇dx:x1-x0,
        dy:y1-y0,
        d:2*dy-dx,
        y=y0◇
      (loop for x from x0 to x1
            do #◇a[x,y]:1,
                 if d>0 then
                   (y:y+1,
                    d:d-2*dx),
                 d:d+2*dy◇))

you can make the code above fully operational in common lisp using dispatch macro on a unicode character, so i've been experimenting with such infix mode in my private code. i'll leave the judgement over whether or not this increases readibility.