Forcing type conversions

Forced type conversions in C + +: static_cast, reinterpret_cast, Const_cast, Dynamic_cast.static_cast: For conversions between non-polymorphic types (static transformations), it can be used between any standard type, However, it cannot be used for conversions between unrelated types. Static_cast can only be used for conversions between related types. Example:       int i = 2;       Double d = static_cast<double> (i); Correct, correlation type conversion             int *p = &i;       Double d = static_cast<double> (P);//error, cannot convert, do not want to close type reinterpret_ Cast: The operator is used to convert one type to another different type. Example: typedef void (*FUNC) (), int dosomthing (int i) {      cout << " Dosomthing (): "<< i << Endl;       return 0;} void Test () {      FUNC pf = reinterpret_cast<func> (dosomthing);       PF ();} Reinterpret_cast: You can have the compiler look at the dosomething function in a way that is defined by Func, but this sometimes produces indeterminate results. In a word, reinterpret_cast is a very bug. Const_cast: The most common use is to remove the const attribute of a variable to make it easy to assign a value. Example: void Test () {      const int i = Ten,       int* b =const_cast<int *> (&i);       *B = 20;       cout << i << Endl;      //result is 10 because the compiler is optimized, so it will be valued in the register       cout << *b << Endl;    //The result is that 20,b points to I in memory, changing the value in memory}void test () {      volatile const int i = Ten;         int* b =const_cast<int *> (&i);       *b = 20;       cout << i << Endl;      //result is 20 because volatile guarantees memory visibility       cout << *b << Endl;    }dynamic_cast: A pointer or reference to convert a pointer or reference of a parent class object to a subclass object. 1. dynamic_cast can only be used for Class 2 that contains virtual functions, if the parent pointer is to a parent class object, 0 is returned, and if the parent pointer points to the subclass object, the conversion succeeds. Example: void Test () {      A A,       b b,       A *pa = &a;  //is correct, the parent pointer points to the parent Class object       PA = &b;     Correct, parent pointer pointing to subclass object      //b *PB = &a; &NBSP;//C Error, sub-class pointer to parent class object       B *PB = &b;      //is correct, the sub-class pointer points to the subclass object}void Fun (A *pa) {      B *PB = dynamic_cast<b *>(p a);        //if the PA points to the parent class object, returns 0 if it points to a subclass object, successfully converted       cout << "PB1:" << pb<< E NDL;} void Test () {      a A;       b b;       Fun (&a)       &N Bsp         cout << &a << Endl;       Fun (&b);       cout << &b<< Endl;} Explicit: Preventing implicit type conversions by constructors: Class A{public:       A (int a)             : _a (0) {}       A (const a& a)       {     }private:       int _a;}; void Test () {      a A1 (1);  //Direct initialization      //1 implicitly converted to a TMP (1), a A2 (TMP)     &N Bsp A A2 = 1;      //correct}class a{public:       Explicit A (int a)              :_a (0) {}       A (const a& a)     &NBSp {     }private:       int _a;}; void Test () {      a A1 (1);  //Direct initialization      //1 implicitly converted to a TMP (1), a A2 (TMP)     &N Bsp A A2 = 1;    //Error} If you do not want to generate intermediate objects, you can declare explicit before the constructor.

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Forcing type conversions