ex 3.20 - working
ex 3.20 - done
3.3.2 - queue abstraction
3.3.2 - code copied, want some test...
3.3.2 - queue example
3.3.2 - few comment, + readability
ex 3.21 - startup ...
seperate queue impl as lib
ex 3.21 - reproduce problem
ex 3.21 - explanation
ex 3.21 - done
ex 3.22 - startup
ex 3.22 - proxies
ex 3.22 - done
ex 3.23 - abstraction
ex 3.23 - front-insert
ex 3.23 - I think it won't work
ex 3.23 - rewrite insert
ex 3.23 - front/rear insert
ex 3.23 - impl done