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The std::string type is the main string datatype in standard C++ since 1998, but it was not always part of C++. From C, C++ inherited the convention of using null-terminated strings that are handled by a pointer to their first element, and a library of functions that manipulate such strings.
The length of a string is the number of code units before the zero code unit. [1] The memory occupied by a string is always one more code unit than the length, as space is needed to store the zero terminator. Generally, the term string means a string where the code unit is of type char, which is exactly 8 bits on all modern machines.
A pointer can be declared as a const pointer to writable value, or a writable pointer to a const value, or const pointer to const value. A const pointer cannot be reassigned to point to a different object from the one it is initially assigned, but it can be used to modify the value that it points to (called the pointee).
String representation Object copy Value equality Object comparison Hash code Object ID Human-readable Source-compatible ABAP Objects — APL (Dyalog) ⍕x ⎕SRC x ⎕NS x: x = y — C++ x == y [52] pointer to object can be converted into an integer ID: C# x.ToString() x.Clone() x.Equals(y) x.CompareTo(y) x.GetHashCode()
A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type.
Non-static member functions (instance methods) have an implicit parameter (the this pointer) which is the pointer to the object it is operating on, so the type of the object must be included as part of the type of the function pointer. The method is then used on an object of that class by using one of the "pointer-to-member" operators: .* or ...
An allocator, A, for objects of type T must have a member function with the signature A:: pointer A:: allocate (size_type n, A < void >:: const_pointer hint = 0). This function returns a pointer to the first element of a newly allocated array large enough to contain n objects of type T ; only the memory is allocated, and the objects are not ...
Notice that the object pointed by an auto_ptr is destroyed using operator delete; this means that you should only use auto_ptr for pointers obtained with operator new. This excludes pointers returned by malloc/calloc/realloc, and pointers to arrays (because arrays are allocated by operator new[] and must be deallocated by operator delete[]).