−1 This won't respond to the concern from the title, “When is #contain library required in C++?”. I suppose that that could well be Alright Together with the OP. But it's problem when this concern is utilized as referent for just a close-as-replicate of some other problem. Jay 37.1k33 https://directoryio.com/listings1560659/getting-my-best-music-websites-for-write-song-lyrics-to-work