What's the difference between generators, coroutines, and continuations?

generators
- they can only return multiple times (like a read-only pipe) — they can't be called multiple times (like a writable pipe)
coroutines
- they're like a pipe that can be written to, as well as read from
- they're equivalent to fibers (as long as the language allows fine-grained control of fibers)
- the word "coroutine" can encompass widely varying functionality -- see chapter2 here for a classification of them
  - 2.1. asymmetric vs symmetric
    - asymmetric — subordinate and caller
    - symmetric — operate at the same hierarchical level
  - 2.2 first-class vs constrained
    - first-class —
    - constrained — can only be used for iterators/generators
  - 2.3 stackful vs not stackful
    - stackful — it can yield from lower levels (e.g. inside for-loops, etc)
    - not stackful — it can only resume from the top-level that it was started from
  - 2.4 full coroutines — both 1) first-class, and 2) stackful
continuations
- they're the ultimate in execution-flow-control
- explanations that make the most sense to me: [1] [2] [3]