Static Cast

///////////////////////////////////////
// StaticCastDemo.cpp: demostrates static cast,including promotion constructor
// and cast operator
// Author: Yu Zhang
// Org: Syracuse University
// Contact: 315-314-0228
///////////////////////////////////////

/*
  Static Cast
---------------
toType toObject = static_cast<toType>(fromObject);

Creates toObject by calling promotion constructor from toType
  toType::toType(fromType fromObject);
or
  cast operator from fromType
 */

#include <iostream>
using namespace std;



class fromType; //forward declaration needed by toType constructor

class toType
{
public:
  inline toType(){cout<<"void constructor of toType is called \n";}
  //promotion constructor
   explicit toType(const fromType& fromObject); //keyword explicit declares this constructor to be non-converting,so that
                                         //avoid silent converting
  inline toType(const toType& toObject){cout<<"copy constructor of toType is called \n";}
};

// promotion constructor of toType
toType::toType(const fromType& fromObject)
{
  cout<<"promotion constructor of toType is called \n";
}

class fromType
{
public:
  fromType(){
    cout<<"void constructor of fromType is called \n";
  }
  operator toType();
};

//
fromType::operator toType(){
  cout<<"cast operator of fromType is called\n";
  return toType();
}





int main()
{
  fromType fromObject;//void constructor of fromType will be called
  toType toObject = static_cast<toType>(fromObject);//Precedency: promotion constructor of toType will be called if it
                                                  //is defined, if not, cast operator of fromType will be called
  toType toObject_another = fromObject; // only cast operator of fromType will be called
  //note: no copy constructor is called during casting
  return 0;
}

-------------------------------------------------------------------------
output:

void constructor of fromType is called
promotion constructor of toType is called
cast operator of fromType is called
void constructor of toType is called

-------------------------------------------------------------------------

if promotion constructor of toType is not implemented, say we commented the code part of it, then only cast operator of fromType will be called  .

output:

void constructor of fromType is called
cast operator of fromType is called
void constructor of toType is called
cast operator of fromType is called
void constructor of toType is called