Chapter 3. Moving to Modern C++ Flashcards
Item 7: Distinguish between () and {} when creating objects.
Braced initialization is the most widely usable initialization syntax, it prevents narrowing conversions, and it’s immune to C++’s most vexing parse.
During constructor overload resolution, braced initializers are matched to std::initializer_list parameters if at all possible, even if other constructors offer seemingly better matches.
An example of where the choice between parentheses and braces can make a significant difference is creating a std::vector with two arguments.
Choosing between parentheses and braces for object creation inside templates can be challenging.
Item 8: Prefer nullptr to 0 and NULL.
Prefer nullptr to 0 and NULL.
Avoid overloading on integral and pointer types.
Item 9: Prefer alias declarations to typedefs.
typedefs don’t support templatization, but alias declarations do.
Alias templates avoid the “::type” suffix and, in templates, the “typename” prefix often required to refer to typedefs.
C++14 offers alias templates for all the C++11 type traits transformations.
Item 10: Prefer scoped enums to unscoped enums.
C++98-style enums are now known as unscoped enums.
Enumerators of scoped enums are visible only within the enum. They convert to other types only with a cast.
Both scoped and unscoped enums support specification of the underlying type. The default underlying type for scoped enums is int. Unscoped enums have no default underlying type.
Scoped enums may always be forward-declared. Unscoped enums may be forward-declared only if their declaration specifies an underlying type.
Item 11: Prefer deleted functions to private undefined ones.
Prefer deleted functions to private undefined ones.
Any function may be deleted, including non-member functions and template instantiations.
Item 12: Declare overriding functions override.
Declare overriding functions override.
Member function reference qualifiers make it possible to treat lvalue and rvalue objects (*this) differently.
Item 13: Prefer const_iterators to iterators.
Prefer const_iterators to iterators.
In maximally generic code, prefer non-member versions of begin, end, rbegin, etc., over their member function counterparts.
Item 14: Declare functions noexcept if they won’t emit exceptions.
noexcept is part of a function’s interface, and that means that callers may depend on it.
noexcept functions are more optimizable than non-noexcept functions.
noexcept is particularly valuable for the move operations, swap, memory deallocation functions, and destructors.
Most functions are exception-neutral rather than noexcept.
Item 15: Use constexpr whenever possible.
constexpr objects are const and are initialized with values known during compilation.
constexpr functions can produce compile-time results when called with arguments whose values are known during compilation.
constexpr objects and functions may be used in a wider range of contexts than non-constexpr objects and functions.
constexpr is part of an object’s or function’s interface.
Item 16: Make const member functions thread safe.
Make const member functions thread safe unless you’re certain they’ll never be used in a concurrent context.
Use of std::atomic variables may offer better performance than a mutex, but they’re suited for manipulation of only a single variable or memory location.
Item 17: Understand special member function generation.
The special member functions are those compilers may generate on their own: default constructor, destructor, copy operations, and move operations.
Move operations are generated only for classes lacking explicitly declared move operations, copy operations, and a destructor.
The copy constructor is generated only for classes lacking an explicitly declared copy constructor, and it’s deleted if a move operation is declared. The copy assignment operator is generated only for classes lacking an explicitly declared copy assignment operator, and it’s deleted if a move operation is declared. Generation of the copy operations in classes with an explicitly declared copy operation or destructor is deprecated.
Member function templates never suppress generation of special member functions.
