Thread: Classes or Structs faster for Lists

Class defaults to private, constructors can be private/protected.

Code:

struct blah {
private:
 int a;
};

class blah2 {
 blah2() { }  // legal, private constructor
};

int main() {
 blah inst;
// blah2 inst2; // illegal.. can't call private constructorf
 return 0;
}

Private constructors are neccesary for the singleton design pattern.

omg, i cant believe you people post before not testing it first:
here is an EXAMPLE of a private struct:

struct mystr{
private:
int ignorant;
public:
void set(int);
int get(void);
};

THERE YA GO A PRIVATIZED STRUCT.. so simple its hurting.

ROD PLEASE GO LEARN C++. And learn to read, i said structs CANNOT inherit.

ALSO, CLASS DEFAULT TO PRIVATE, YES THEY DO, UNLESS YOU SPECIFY IT TO BE PUBLIC. ITS PRIVATE!!!!!
geez people test ur code first.

I was just showing that it was legal to have private constructors. There are real uses for private constructors... ala that singleton design pattern.

http://www.google.com/search?q=singleton+design+pattern

I've never used structs with private members.. usually structs have some minimal amount of implementation (perhaps a couple convienent constructors)and serve as little more than data aggregates.

The keyword struct means different things in C++ than in C. It is used differently as well, although the general idea remains the same. I don't do much C programming, and I don't have my C reference here at work so I can't gaurantee the accuracy of the following, however, I should be pretty close:

Code:

//declaration of a struct type in C
typedef struct cStruct
{
  int data;
  char name[80];
  //no functions possible in here
};

//declaration of a C struct variable in a program
int main()
{
  struct cStruct myStruct;
  //etc.


declaration of a struct type in C++
struct cppStruct
{
  int data;
  char name[80];
  void showMembers();
};


//declaration of C++ struct variable in a program
int main()
{
  cppStruct myStruct;
  //etc.

in C++ the only difference between a struct and a class is that the members of a struct are public by default and the members of a class are private by default. Therefore you can have inheritiance of a struct in C++, just like you can with a class. It is not commonly done, because most programmers use structs in C++ similar to the way they are used in C out of convention/respect, but there is no inherent restriction in the language itself as far as I know. It should be easy enough to check.

Code:

/*
program demonstrating inheritance using a struct, proving the members of a struct are public by default, and members of a class are private by default.
*/

#include <iostream.h>

struct Base
{
  //all members default to public access
  int bData;
  Base();
};

struct BaseChild : public Base
{
    //these are still public by default
    BaseChild();
    int showData();
    
    //bData will be inherited as public by default as well.
    
    //using private access for protection of data in a struct
    private:
        int bcData;
};

Base::Base() : bData(23)
{}

BaseChild::BaseChild()
{
   bcData = 101;
}

int BaseChild::showData()
{
   return bcData;
}

class MyClass
{
   //using default private access on purpose
   int cData;

   public:
      int showData();
};

MyClass::MyClass() : cData(4)
{}

int MyClass::showData()
{
   return cData;
}

int main()
{
  BaseChild baseChild;
  MyClass myClass;
  
  cout << "bData in baseChild is inherited, public and = "
           << baseChild.bData << endl; 

  //this line should cause compiler error so comment it out once 
  //it gives compiler error
  cout << "bcData in baseChild using public access = " 
          << baseChild.bcData << endl;
  
  cout << "bcData in baseChild using public accessor function  = "
          << baseChild.showData() << endl;
  
  //this line should cause compiler error, too.  so comment it out.
  cout << "cData in myClass object is "  << myClass.cData << 
                 endl; 
  
  cout << "using public accessor function cData in myClass is " 
          <<  myClass.showData() << endl;
 
  return 0;
}

Will try to compile at home when I have compiler available. For now code not tested by fire.