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You want to separate memory allocation from construction e.g. in implementing a std::vector<> (see std::vector<>::reserve). The basic problem is that the constructor is a peculiar function; when it starts off, there is no object, only raw memory. And by the time it finishes, you have a fully initialized object.
Delayed evaluation solves this problem, and can be implemented in C++ by letting operator+ return an object of an auxiliary type, say VecSum, that represents the unevaluated sum of two Vecs, or a vector with a VecSum, etc. Larger expressions then effectively build expression trees that are evaluated only when assigned to an actual Vec variable ...
All logical operators exist in C and C++ and can be overloaded in C++, albeit the overloading of the logical AND and logical OR is discouraged, because as overloaded operators they behave as ordinary function calls, which means that both of their operands are evaluated, so they lose their well-used and expected short-circuit evaluation property ...
For example, a container defined as std::vector<Shape*> does not work because Shape is not a class, but a template needing specialization. A container defined as std::vector<Shape<Circle>*> can only store Circles, not Squares. This is because each of the classes derived from the CRTP base class Shape is a unique type.
In C++11, a move constructor of std::vector<T> that takes an rvalue reference to an std::vector<T> can copy the pointer to the internal C-style array out of the rvalue into the new std::vector<T>, then set the pointer inside the rvalue to null. Since the temporary will never again be used, no code will try to access the null pointer, and ...
Added in C++26. Provides the class std::inplace_vector, analogous to std::vector with a fixed capacity defined at compile time. <map> Provides the container class templates std::map and std::multimap, sorted associative array and multimap. <mdspan> Added in C++23. Provides the class template std::mdspan, analogous to std::span but the view is ...
The C++ standard library instead provides a dynamic array (collection) that can be extended or reduced in its std::vector template class. The C++ standard does not specify any relation between new / delete and the C memory allocation routines, but new and delete are typically implemented as wrappers around malloc and free. [6]
In C++ a std::vector object supports the store, select, and append operations with the performance characteristics discussed above. Vectors can be queried for their size and can be resized. Slower operations like inserting an element in the middle are also supported.