Summary of references in C + +

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(1) In the use of reference, it is meaningless to simply give a certain variable name, the purpose of the reference is mainly used in the transfer of function parameters, to solve the problem of the transfer efficiency and the space of large data or objects.

(2) using the parameters of the reference transfer function, it can ensure that the parameters are not generated in the transfer of the copy, improve the efficiency of the transfer, and through the use of const, to ensure the security of reference delivery.

(3) The difference between a reference and a pointer is that the pointer is indirectly manipulated by the variable it points to after it points to an object through a pointer variable. The use of pointers in the program, the readability of the program, and the reference itself is the alias of the target variable, the operation of the reference is the operation of the target variable.

(4) The timing of the use of references. Reference is recommended for the stream operator << and >>, the return value of the assignment operator =, the parameter of the copy constructor, the parameter of the assignment operator =, and other cases.

(1) The effect of passing a reference to a function is the same as passing a pointer. At this point, the parameter of the function is used as the real parametric or an alias of the object in the original central melody function, so the operation of the parameter variable in the function is the operation of its corresponding target object (in the central Melody function).

(2) using the parameters of the reference transfer function, in memory does not produce a copy of the argument, it is directly to the actual parameter operation, while using the general variable transfer function parameters, when a function call, you need to assign a storage unit to the parameter, the parameter variable is the copy of the argument variable; Therefore, when the parameter passes the data is large, uses the reference to pass the parameter with the general variable efficiency and occupies the space to be good.

(3) The use of pointers as parameters of the function, although also can achieve with the use of reference, but in the function of the parameter allocation of the same storage unit, and the need to re-use "* pointer variable name" in the form of operations, which is prone to error and poor program reading; On the other hand, at the call point of the keynote function You must use the address of the variable as the argument. And references are easier to use and clearer.

If you need to use reference to improve the efficiency of the program, but also to protect the data passed to the function is not changed in the function, you should use the common reference

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