The answer available at http://www.stroustrup.com/bs_faq.html#How-long is:
That depends on what you mean by “learning.” If you are a C programmer you can learn enough C++ to make you more effective at C-style programming in a day.
He also says in http://www.stroustrup.com/learn.html that
Most experienced programmers I have talked with quotes times from a half year to one and a half year for becomming really comfortable with C++ and the key data abstraction and object- oriented techniques it supports.
It will be two years next week since I restarted ham radio, so it is almost time that I feel comfortable with CW conversation.
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