I retired from active involvement in C++ at the end of 2015, and in the ensuing two and a half years, I’ve forgotten enough details of the language that I am no longer able to properly evaluate bug reports regarding the technical aspects of my books. C++ is a large, intricate language with features that interact in complex and subtle ways, and I no longer trust myself to keep all the relevant facts in mind.
In case you don’t know him, he’s not particularly old (born 1959, which makes him 59 as of this writing), and in good health as far as I know. So this is a statement about the complexity of C++, and not about Scott Meyers, who is still as sharp and brilliant as the day he retired.
One of the criticisms of C++ has always been its complexity. There are so many “gotchas,” special cases, and unexpected side-effects that it seems impossible that a single person could keep it all in her head. This seems like a good illustration of the extent to which that is true.