C++98 had a single set of rules for type deduction: the one for function templates.
C++11 modifies that ruleset a bit and add two more, one for auto and one for decltype.
C++14 then extends the usage contexts in which auto and decltype may be employed. (查看原文)
When users of a complex system are ignorant of how it works, yet happy with what it does, that says a lot about the design of the system.
By this measure, template type deduction in C++ is a tremendous success. (查看原文)
The only real difference between auto and template type deduction is that auto assumes that a braced initializer represents a std::initializer_list, but the template type deduction doesn't. (查看原文)
The use of "decltype(auto)" is not limited to function return type. I can also be convenient for declaring variables when you want to apply the decltype type deduction rules to the initializing expression. (查看原文)
Employing pass-by-value for objects of an unknown type generally risks the performance hit of unnecessary copying, the behavioral problems of object slicing, and ... (查看原文)
As a general rule, "invisible" proxy classes don't play well with auto.
Objects of such classes are often not designed to live longer than a single statement, so creating variables of those types tends to violate fundemental library design assumptions. (查看原文)
Braces-by-defult folks are attracted by their unrivaled breadth of applicability, their prohibition of narrowing conversions, and their immunity to C++'s most vexing parse.
The parentheses crowd are attracted to tis consistency with the C++ 98 syntactic tradition, its avoidance of the auto-deduced-a-std::initializer_list problem, and the knowledge that their object creation calls won't be inadvertently waylaid by std::initializer_list constructors. (查看原文)
