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Type Casting in C++ (static, dynamic, reinterpret & const_cast)


Four type casting operators in C++ is listed below:
static_cast -> To convert non polymorphic types.
const_cast -> To add or remove the const-ness or volatile-ness type.
dynamic_cast -> To convert polymorphic types.
reinterpret_cast -> For type conversion of unrelated types.

Example of static_cast :-

#include <iostream.h> #include <stdlib.h> int main() { int sum = 1000; int count = 21; double average1 = sum/count; cout<<"Before conversion = "<<average1<<endl; double average2 = static_cast<double>(sum)/count; cout<<"After conversion = "<<average2<<endl; system("pause"); return 0; } Example of const_cast :- //demonstrates const_cast #include <iostream.h> #include <stdlib.h> int main() { //p = 10 is a constant value, cannot be modified const int p = 20; cout<<"const p = "; cout<<p; cout<<"\nq = p + 20 = "; cout<<(p + 20)<<endl; //The following code should generate error, because //we try to modify the constant value... //uncomment, recompile and re run, notice the error... //p = 15; //p++; //remove the const... int r = const_cast<int&> (p); //the value of 10 should be modified now... --r; cout<<"Removing the const, decrement by 1,\nNew value = "<<r<<endl; system("pause"); } Example of Dynamic cast :- //upcast conversion using dynamic_cast #include <iostream.h> #include <stdlib.h> //base class class Base1 {}; //derived class... class Derived1:public Base1 {}; //another derived class class Derived2:public Derived1{}; //dynamic_cast test function... void funct1() { //instantiate an object… Derived2* Test1 = new Derived2; //upcasting, from derived class to base class, //Derived1 is a direct from Base1 //making Test2 pointing to Derived1 sub-object of Test1 Derived1* Test2 = dynamic_cast<Derived1*>(Test1); cout<<"Derived1* Test2 = dynamic_cast<Derived1*>(Test1);"<<endl; if(!Test2) cout<<"The conversion is fail..."<<endl; else cout<<"The conversion is successful..."<<endl; //upcasting, from derived class to base class //Derived2 is an indirect from Base1 Base1* Test3 = dynamic_cast<Derived1*>(Test1); cout<<"\nBase1* Test3 = dynamic_cast<Derived1*>(Test1);"<<endl; if(!Test3) cout<<"The conversion is fail..."<<endl; else cout<<"The conversion is successful..."<<endl; } int main() { funct1(); system("pause"); return 0; } Example of reinterpret_cast :- //unsigned int pointers conversion #include <iostream.h> #include <stdlib.h> unsigned int* Test(int *q) { //convert int pointer to unsigned int pointer unsigned int* code = reinterpret_cast<unsigned int*>(q); //return the converted type data, a pointer... return code; } int main(void) { //array name is a pointer... int a[10]; cout<<"int pointer unsigned int pointer"; for(int i = 0;i<=10;i++) cout<<(a+i)<<" converted to: "; cout<<Test(a+i); system("pause"); return 0; }