non-oriented infix = and ~= (output only);
added case_split (with case names);
By chapter:chapters 1 and 2, maybe 3: Peter Whitechapters 6, 7 and 8: David von Oheimchapter 6, maybe 8: Gerwin Kleinchapters 3, maybe 4: Tanja Voschapters 1-3 at least: Stefano Bistarelli