1.1.5.3 Explicit conversion

• There exist two main syntax for generic type-casting: functional and c-like:
  double x = 10.3; 
  int y; 
  unsigned int n1 = (unsigned int)f; // C-style cast 
  unsigned int n2 = unsigned(f);     // functional cast 
  //functional cast only be used in one word type. 
  //unsigned int (f)  is not right, 
  //int *(f) is not right either.
• Unrestricted explicit type-casting allows to convert any pointer into any other pointer type, independently of the types they point to. (syntax and compiling is right, but cause runtime error).
  char c = 10;       // 1 byte 
  int *p = (int*)&c; // compile ok 
  *p = 5 //runtime error, stack corruption. 
   
  int *p = static_cast<int*>(&c) comple error;
• There are three operators, dynamic_cast, const_cast and static_cast. You should use dynamic_cast, static_cast and const_cast firstly in C++. Why? see below explanation.
• dynamic_cast use to cast down a base pointer to child pointer. dynamic_cast assure that down cast is valid. Because you can always safely assign child pointer to base pointer in C++. (That is how polymorphic implement.) const_cast will remove cast feature.
• static_cast<type-name> expression will be valid only if type-name can be converted implicitly to the same type that expression has. It will stop you from change a bird class to an apple class which are two totally unrelated classes. Even change int to double, encourage you to use static_cast<double>(i). it also can help you to find cast easily in you source code by search "static_cast".