How the STL Uses Explicit

The discussion at the WG21 meeting in St. Louis includes a paper on the policy for using the `explicit` keyword in C++ proposals. The aim is to establish a style guide for proposal authors to ensure consistency and avoid repeated discussions on the same topics. While the author suggests that all constructors should be explicit by default in industry code, exceptions exist in the 40-year-old Standard Library, like the non-explicit iterator-pair constructor of `std::vector`. The guidelines for the Standard Library differ from industry practices and focus on types aiming to enter the library. Specific rules are outlined for operator conversions, constructors based on arity, and deviations permitted with justifications. The document emphasizes the importance of maintaining consistency in C++ to prevent potential compiler errors. The guidelines are subject to updates, with future revisions expected to be adopted by the committee for standardization.