add looking Chap09 p151 L9 and keep-looking Chap09 p152 L7
add eternity Chap09 p153 L8
add shift Chap09 p154 L3
add align Chap09 p154 L5
add length* Chap09 p155 L4
add weight* Chap09 p156 L1
add shuffle Chap09 p156 L6
add C (Collatz) Chap09 p157 L7
add A (Ackermann) Chap09 p158 L3
add will-stop? Chap p159 L4
add last-try Chap09 p160 L4