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In the C++ programming language, the assignment operator, =, is the operator used for assignment.Like most other operators in C++, it can be overloaded.. The copy assignment operator, often just called the "assignment operator", is a special case of assignment operator where the source (right-hand side) and destination (left-hand side) are of the same class type.
The move assignment operator, like most C++ operators, can be overloaded. Like the copy assignment operator it is a special member function . If the move assignment operator is not explicitly defined, the compiler generates an implicit move assignment operator ( C++11 and newer) provided that copy / move constructors , copy assignment operator ...
Copy constructor if no move constructor and move assignment operator are explicitly declared. If a destructor is declared generation of a copy constructor is deprecated (C++11, proposal N3242 [2]). Move constructor if no copy constructor, copy assignment operator, move assignment operator and destructor are explicitly declared.
Copy assignment operator – assign all the object's members from the corresponding members of the assignment operator's argument, calling the copy assignment operators of the object's class-type members, and doing a plain assignment of all non-class type (e.g. int or pointer) data members.
At the lowest level, assignment is implemented using machine operations such as MOVE or STORE. [2] [4] Variables are containers for values. It is possible to put a value into a variable and later replace it with a new one. An assignment operation modifies the current state of the executing program. [3]
A unique_ptr explicitly prevents copying of its contained pointer (as would happen with normal assignment), but the std::move function can be used to transfer ownership of the contained pointer to another unique_ptr. A unique_ptr cannot be copied because its copy constructor and assignment operators are explicitly deleted.
The vector maintains a certain order of its elements, so that when a new element is inserted at the beginning or in the middle of the vector, subsequent elements are moved backwards in terms of their assignment operator or copy constructor. Consequently, references and iterators to elements after the insertion point become invalidated.
For example, += and -= are often called plus equal(s) and minus equal(s), instead of the more verbose "assignment by addition" and "assignment by subtraction". The binding of operators in C and C++ is specified (in the corresponding Standards) by a factored language grammar, rather than a precedence table. This creates some subtle conflicts.