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In the C++ programming language, special member functions [1] are functions which the compiler will automatically generate if they are used, but not declared explicitly by the programmer. The automatically generated special member functions are: Default constructor if no other constructor is explicitly declared.
The rule of three (also known as the law of the big three or the big three) is a rule of thumb in C++ (prior to C++11) that claims that if a class defines any of the following then it should probably explicitly define all three: [1] destructor; copy constructor; copy assignment operator; These three functions are special member functions. If ...
/* will print the provided char string as expected using ADL derived from the argument type std::cout */ operator << (std:: cout, "Hi there") /* calls a ostream member function of the operator<< taking a void const*, which will print the address of the provided char string instead of the content of the char string */ std:: cout. operator ...
C++14 allows the lookup to be done via an arbitrary type, so long as the comparison operator can compare that type with the actual key type. [16] This would allow a map from std::string to some value to compare against a const char* or any other type for which an operator< overload is available.
The following is a declaration of the concept "equality_comparable" from the <concepts> header of a C++20 standard library. This concept is satisfied by any type T such that for lvalues a and b of type T, the expressions a==b and a!=b as well as the reverse b==a and b!=a compile, and their results are convertible to a type that satisfies the concept "boolean-testable":
To elaborate on the above example, consider a base class with no virtual functions. Whenever the base class calls another member function, it will always call its own base class functions. When we derive a class from this base class, we inherit all the member variables and member functions that were not overridden (no constructors or destructors).
Searching algorithms like binary_search and lower_bound use binary search and like sorting algorithms require that the type of data must implement comparison operator < or custom comparator function must be specified; such comparison operator or comparator function must guarantee strict weak ordering.
Any derived class inherits the virtual function as pure and must provide a non-pure definition of it (and all other pure virtual functions) before objects of the derived class can be created. A program that attempts to create an object of a class with a pure virtual member function or inherited pure virtual member function is ill-formed.