1.1.5.2 Explicit numerical conversion

• In order to depress conversion warning, you can use explict numerical conversion to state your intention clearly and loudly.
• In C language, there exist two main syntax for generic type-casting: functional and C-style cast. Prefer C-style cast
  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.