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auto and decltype
auto is more than just a shortcut to avoid writing types—it has complete deduction rules, proxy-type pitfalls, and consistency with template deduction. decltype is the cornerstone of template metaprogramming, allowing us to precisely obtain the type of an expression. C++17's CTAD makes template argument deduction more concise than ever. In this chapter, we thoroughly cover the three dimensions of type deduction: auto, decltype, and CTAD.