How to make multiple "objects" (classes question) easy.

This is a discussion on How to make multiple "objects" (classes question) easy. within the C++ Programming forums, part of the General Programming Boards category; for example Code: for(t = 0; t<100; t++){ sands[t] = new sand(10,t) } I was wondering how you can use ...

  1. #1
    Registered User
    Join Date
    Mar 2009
    Posts
    76

    How to make multiple "objects" (classes question) easy.

    for example
    Code:
    for(t = 0; t<100; t++){
    sands[t] = new sand(10,t)
    }
    I was wondering how you can use the same function like that. The above wont work. And yes it is defined:
    Code:
    class Dot
    {
        private:
        int x, y;
        int xVel, yVel;
        public:
        Dot(int x,int y);
        void fall();
        void move();
        void show();
        void setxy(int xx,int yy);
    };
    
    Then those functions are further defined
    I might have to explain my problem better...

  2. #2
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    23,773
    One way is to define a function object:
    Code:
    class MakeDot
    {
    public:
        MakeDot(int x) : x(x), y(0) {}
    
        Dot operator()()
        {
            return Dot(x, y++);
        }
    private:
        int x;
        int y;
    };
    Then you use the function object in conjunction with std::generate_n(), e.g.,
    Code:
    std::vector<Dot> sands;
    std::generate_n(std::back_inserter(sands), 100, MakeDot(10));
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Registered User
    Join Date
    Mar 2009
    Posts
    76
    In my first example...
    Where would I define the "sands" thing?

  4. #4
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    23,773
    Quote Originally Posted by azjherben
    Where would I define the "sands" thing?
    Um, you would define it before you use it.

    On a hunch, are you a Java programmer? I have a feeling that you are unnecessarily and incorrectly using new due to such a background.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Easy String position question...
    By Striph in forum C Programming
    Replies: 4
    Last Post: 05-11-2009, 08:48 PM
  2. Beginner Classes Question
    By kbro3 in forum C++ Programming
    Replies: 9
    Last Post: 08-14-2008, 07:43 AM
  3. Curiosity question about classes...
    By Raigne in forum C++ Programming
    Replies: 5
    Last Post: 03-10-2008, 12:34 PM
  4. A very long list of questions... maybe to long...
    By Ravens'sWrath in forum C Programming
    Replies: 16
    Last Post: 05-16-2007, 05:36 AM
  5. Multiple Inheritance - Size of Classes?
    By Zeusbwr in forum C++ Programming
    Replies: 10
    Last Post: 11-26-2004, 08:04 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21