modify multirember Chap12 p17 L4
modify length (olength) Chap12 p17 L5 (left)
modify length (olength) Chap12 p17 L5 (right)
modify multirember Chap12 p18 L3 (left)
modify multirember Chap12 p18 L3 (right)
modify multirember Chap12 p20 L6
add mrpie Chap12 p21 L6

temporal function only used for explanation
reverting multirember Chap12 p21 L7
modify multirember Chap12 p22 L1
remind multirember-f Chap12 p23 L5
modify multirember-f Chap12 p24 L4
modify multirember Chap12 p25 L1
modify multirember Chap12 p25 L4
modify multirember Chap12 p26 L1
remind member? Chap12 p26 L2
modify member? Chap12 p27 L1 (left)
modify member? Chap12 p27 L1 (right)
remind union Chap12 p27 L5
modify union Chap12 p28 L2
modify union Chap12 p28 L3