private bool function

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  • 2005
    #1

    private bool function

    Hi

    I have a little trouble with this code.

    There is a calss with

    Class xxx{
    public:
    ----
    ----

    private:
    bool Full () { return (............ true : false) ;}

    };

    I want to call/use the "Full" above in a the main or in a subroutine.

    How do I go about?

    Thanks

    Tags: None
    • Marcus Kwok
      #2
      Re: private bool function

      2005 <uws2003@yahoo. comwrote:
      There is a calss with
      >
      Class xxx{
      public:
      ----
      ----
      >
      private:
      bool Full () { return (............ true : false) ;}
      >
      };
      >
      I want to call/use the "Full" above in a the main or in a subroutine.
      >
      How do I go about?
      Since Full() is private, you can only call it from within class xxx. If
      you want to call it from outside of the class, you need to make
      something a friend of class xxx.

      Also, when posting code, please post real C++ code.

      --
      Marcus Kwok
      Replace 'invalid' with 'net' to reply

        Comment

        • Clark S. Cox III
          #3
          Re: private bool function

          2005 wrote:
          Hi
          >
          I have a little trouble with this code.
          >
          There is a calss with
          >
          Class xxx{
          public:
          ----
          ----
          >
          private:
          bool Full () { return (............ true : false) ;}
          >
          };
          >
          I want to call/use the "Full" above in a the main or in a subroutine.
          >
          How do I go about?
          >
          Thanks
          >
          You can't. That is the point of "private:".

          --
          Clark S. Cox III
          clarkcox3@gmail .com

            Comment

            • osmium
              #4
              Re: private bool function

              "2005" wrote:
              I have a little trouble with this code.
              >
              There is a calss with
              >
              Class xxx{
              public:
              ----
              ----
              >
              private:
              bool Full () { return (............ true : false) ;}
              >
              };
              >
              I want to call/use the "Full" above in a the main or in a subroutine.
              >
              How do I go about?
              You don't. When you said it was private you actually meant it was private
              so main (a non-member function) can not access it.

              It is just possible there may be some convoluted way; the designers make a
              point of saying the intent was to deter accidental misuse, not malicious,
              intentional spying. But that is clearly not what you want.


                Comment

                • 2005
                  #5
                  Re: private bool function


                  Marcus Kwok wrote:
                  2005 <uws2003@yahoo. comwrote:
                  There is a calss with

                  Class xxx{
                  public:
                  ----
                  ----

                  private:
                  bool Full () { return (............ true : false) ;}

                  };

                  I want to call/use the "Full" above in a the main or in a subroutine.

                  How do I go about?
                  >
                  Since Full() is private, you can only call it from within class xxx. If
                  you want to call it from outside of the class, you need to make
                  something a friend of class xxx.
                  >
                  Also, when posting code, please post real C++ code.
                  >
                  #define MAXSIZE 5
                  class CAlley {
                  public:
                  CAlley () : m_pTop(0), mSize(0), mMaxSize(MAXSIZ E) { }
                  ~CAlley () {}
                  int Park(int); // park a car

                  void Retrieve(int, CAlley *); // retrieve a car
                  void Terminate(); // quit the program
                  void Display(char *); // display contents af alley

                  private:
                  void SetTop(CarNode *p){m_pTop=p;} // assign top pointer

                  // check if stack is empty
                  bool Empty(){return ((mSize==0) ? true : false);}

                  // check if stack is full
                  bool Full() {return ((mSize==MAXSIZ E) ? true : false);}

                  int Push(CarNode *); // push one node onto top of stack

                  // CarNode * Pop(); // pop one node from the top of stack

                  CarNode *m_pTop; // pointer to top of Allay (stack)
                  int mSize; // number of nodes in Allay (stack)
                  int mMaxSize; //max number of nodes in Allay (stack)
                  };

                  What should be the syntax to access the Fulleither in main and in
                  function?

                    Comment

                    • Salt_Peter
                      #6
                      Re: private bool function


                      2005 wrote:
                      Marcus Kwok wrote:
                      2005 <uws2003@yahoo. comwrote:
                      There is a calss with
                      >
                      Class xxx{
                      public:
                      ----
                      ----
                      >
                      private:
                      bool Full () { return (............ true : false) ;}
                      >
                      };
                      >
                      I want to call/use the "Full" above in a the main or in a subroutine.
                      >
                      How do I go about?
                      Since Full() is private, you can only call it from within class xxx. If
                      you want to call it from outside of the class, you need to make
                      something a friend of class xxx.

                      Also, when posting code, please post real C++ code.
                      #define MAXSIZE 5
                      class CAlley {
                      public:
                      CAlley () : m_pTop(0), mSize(0), mMaxSize(MAXSIZ E) { }
                      ~CAlley () {}
                      int Park(int); // park a car
                      >
                      void Retrieve(int, CAlley *); // retrieve a car
                      void Terminate(); // quit the program
                      void Display(char *); // display contents af alley
                      >
                      private:
                      void SetTop(CarNode *p){m_pTop=p;} // assign top pointer
                      >
                      // check if stack is empty
                      bool Empty(){return ((mSize==0) ? true : false);}
                      >
                      // check if stack is full
                      bool Full() {return ((mSize==MAXSIZ E) ? true : false);}
                      >
                      int Push(CarNode *); // push one node onto top of stack
                      >
                      // CarNode * Pop(); // pop one node from the top of stack
                      >
                      CarNode *m_pTop; // pointer to top of Allay (stack)
                      int mSize; // number of nodes in Allay (stack)
                      int mMaxSize; //max number of nodes in Allay (stack)
                      };
                      >
                      What should be the syntax to access the Fulleither in main and in
                      function?
                      You could declare the function (any function) as a friend in CAlley.
                      But thats a really dumb thing to do.

                      Function Full() is private for a reason. Whats preventing you from
                      adding a public member function like is_Full()?

                      const int MAXSIZE(5);

                      class CAlley
                      {
                      ... // members
                      public:
                      ...
                      bool is_Full() { return Full(); }
                      private:
                      ...
                      bool Full() {return ((mSize==MAXSIZ E) ? true : false);}
                      };

                      Encapsulation is not meant to be broken or bypassed, its there to be
                      respected.
                      Consider what happens if you make some function foo() a friend of
                      CAlley.
                      What if some smartass modifies the function (which has complete,
                      unrestricted access to CAlley) to change a critical private part in an
                      instance of CAlley?
                      Guess what? Its not the fault of the smartass - its your fault. Period.

                        Comment

                        • Marcus Kwok
                          #7
                          Re: private bool function

                          2005 <uws2003@yahoo. comwrote:
                          #define MAXSIZE 5
                          class CAlley {
                          public:
                          CAlley () : m_pTop(0), mSize(0), mMaxSize(MAXSIZ E) { }
                          ~CAlley () {}
                          int Park(int); // park a car
                          >
                          void Retrieve(int, CAlley *); // retrieve a car
                          void Terminate(); // quit the program
                          void Display(char *); // display contents af alley
                          >
                          private:
                          void SetTop(CarNode *p){m_pTop=p;} // assign top pointer
                          >
                          // check if stack is empty
                          bool Empty(){return ((mSize==0) ? true : false);}
                          >
                          // check if stack is full
                          bool Full() {return ((mSize==MAXSIZ E) ? true : false);}
                          >
                          int Push(CarNode *); // push one node onto top of stack
                          >
                          // CarNode * Pop(); // pop one node from the top of stack
                          >
                          CarNode *m_pTop; // pointer to top of Allay (stack)
                          int mSize; // number of nodes in Allay (stack)
                          int mMaxSize; //max number of nodes in Allay (stack)
                          };
                          >
                          What should be the syntax to access the Fulleither in main and in
                          function?
                          You can make them friends of CAlley:

                          // e.g.,
                          int function(bool);

                          class CAlley {
                          // all the stuff you already have, but add

                          friend int function(bool);

                          friend int main(); // if you are not using command-line parameters
                          friend int main(int argc, char* argv[]); // if you are
                          };

                          Note, that if you do this, then function() and main() will have access
                          to ALL private and protected parts of CAlley, which may or may not be
                          what you really want to do.

                          Another way is to move Full() to the public section of CAlley, or to
                          create a new public function that calls the private version of Full().

                          --
                          Marcus Kwok
                          Replace 'invalid' with 'net' to reply

                            Comment

                            • Daniel T.
                              #8
                              Re: private bool function

                              "2005" <uws2003@yahoo. comwrote:
                              I have a little trouble with this code.
                              >
                              There is a calss with
                              >
                              Class xxx{
                              public:
                              ----
                              ----
                              >
                              private:
                              bool Full () { return (............ true : false) ;}
                              >
                              };
                              >
                              I want to call/use the "Full" above in a the main or in a subroutine.
                              >
                              How do I go about?
                              For whatever reason, the author of the xxx class doesn't think that
                              function is safe to use outside of the class. You should contact the
                              author of the class and ask him about it.

                              --
                              To send me email, put "sheltie" in the subject.

                                Comment

                                • Daniel T.
                                  #9
                                  Re: private bool function

                                  "2005" <uws2003@yahoo. comwrote:
                                  #define MAXSIZE 5
                                  class CAlley {
                                  public:
                                  CAlley () : m_pTop(0), mSize(0), mMaxSize(MAXSIZ E) { }
                                  ~CAlley () {}
                                  int Park(int); // park a car
                                  >
                                  void Retrieve(int, CAlley *); // retrieve a car
                                  void Terminate(); // quit the program
                                  void Display(char *); // display contents af alley
                                  >
                                  private:
                                  void SetTop(CarNode *p){m_pTop=p;} // assign top pointer
                                  >
                                  // check if stack is empty
                                  bool Empty(){return ((mSize==0) ? true : false);}
                                  >
                                  // check if stack is full
                                  bool Full() {return ((mSize==MAXSIZ E) ? true : false);}
                                  >
                                  int Push(CarNode *); // push one node onto top of stack
                                  >
                                  // CarNode * Pop(); // pop one node from the top of stack
                                  >
                                  CarNode *m_pTop; // pointer to top of Allay (stack)
                                  int mSize; // number of nodes in Allay (stack)
                                  int mMaxSize; //max number of nodes in Allay (stack)
                                  };
                                  >
                                  What should be the syntax to access the Fulleither in main and in
                                  function?
                                  Again, if CAlley is your class and you are allowed to make changes and
                                  you don't think it would break anything, simply make the "Full()"
                                  function public.

                                  --
                                  To send me email, put "sheltie" in the subject.

                                    Comment

                                    • Victor Bazarov
                                      #10
                                      Re: private bool function

                                      Daniel T. wrote:
                                      "2005" <uws2003@yahoo. comwrote:
                                      >
                                      >#define MAXSIZE 5
                                      >class CAlley {
                                      >[..]
                                      >>
                                      >// check if stack is empty
                                      >bool Empty(){return ((mSize==0) ? true : false);}
                                      >>
                                      >// check if stack is full
                                      >bool Full() {return ((mSize==MAXSIZ E) ? true : false);}
                                      >[..]
                                      >};
                                      >>
                                      >What should be the syntax to access the Fulleither in main and in
                                      >function?
                                      >
                                      Again, if CAlley is your class and you are allowed to make changes and
                                      you don't think it would break anything, simply make the "Full()"
                                      function public.
                                      Not to mention that both 'Empty' and 'Full' members should be declared
                                      'const':

                                      bool Empty() const { ...
                                      bool Full() const { ...

                                      V
                                      --
                                      Please remove capital 'A's when replying by e-mail
                                      I do not respond to top-posted replies, please don't ask


                                        Comment

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