Newbie question on Structures

This is a discussion on Newbie question on Structures within the C++ Programming forums, part of the General Programming Boards category; Hiya! (Optional reading as I introduce myself) I'm a Java Programmer with a couple years of experience, teaching myself how ...

  1. #1
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    Newbie question on Structures

    Hiya!

    (Optional reading as I introduce myself) I'm a Java Programmer with a couple years of experience, teaching myself how to write C++. I've got a pretty good handle on most of the basic concepts that are common between Java and C++, and I generally learn best by doing rather than reading.(/Introduction off).

    My currect project is to create a "Galaxy" of random types of stars, each containing a system of planets of variable type and size.

    I currently have code that functions well that creates the stars by color and sorts them. But to progress further, I am stuck. At some point later I will be assigning each of these stars a random name, but haven't implemented that yet.

    My question: I was thinking, that the easiest way for me to do this effectively would be first to create a Structure Planet which would contain variables Planet Size and Planet Envrionment, and then create another Structure Starsystem which would contain a variable number of the Planet Structures.

    Is this legal in C++? To place one Structure within another Structure? For example...

    Code:
                Struct Planet
                {
                   int planetsize;
                   int planetenv;
                 }
    
                Struct Starsystem
                {
                  int num_planets;
                  Planet insystem[10];
                 }
            
                 Starsystem sol;
                 sol.num_planets = 9;
    Is this legal? If so, how does one access the Structure inside of the Structure?

    Would this work?

    Code:
    sol.insystem[2].size = 100;
    TIA, Structures are pretty new to me in concept and I'm trying to get a grasp of how to use them.

  2. #2
    Software Developer jverkoey's Avatar
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    Would this work?

    Code:

    Code:
    sol.insystem[2].size = 100;
    Yes.

    You're on the right path as far as setting this up. Looks good.

    Welcome to the boards!

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    Ty very much!

    I appriciate it alot

    Glad to see I'm on the right path For a little while there I thought I was baking my brain trying to teach myself!

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    Wait a minute..."Struct"? ....C++ is type sensitive....it has to be "struct".

    Or is that just psuedo-code?

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    TIA, Structures are pretty new to me in concept and I'm trying to get a grasp of how to use them.
    Why? C++ is about using classes not structures. The good news is that the only difference between structures and classes is the default access: in classes if you don't declare the access: e.g. public, private, then it is private by default. With structs the default access is public.

  6. #6
    Seeking motivation... endo's Avatar
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    Quote Originally Posted by Gatt9

    Would this work?

    Code:
    sol.insystem[2].size = 100;
    probably not, you dont have a size variable in Planet - its planetsize.
    Couldn't think of anything interesting, cool or funny - sorry.

  7. #7
    Let's do some coding! Welshy's Avatar
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    I think what your doing there is also called inheritance

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    Quote Originally Posted by 7stud
    Why? C++ is about using classes not structures
    True. Somewhere I read that struct was only there for backward compatibility with C. But in practice, structures usually don't contain member functions... that is, the struct keyword is normally used for C-style structures.

    I don't recommend that people learn C before learning C++ (like I did), but understanding C-style structrues first made classes & objects much easier to understand.

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    but understanding C-style structrues first made classes & objects much easier to understand.
    Java programmers are well aware of what classes and objects are since everything in Java is a class--even main() must be inside a class in Java.

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    C/C++ homeyg's Avatar
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    Quote Originally Posted by Welshy
    I think what your doing there is also called inheritance
    Not quite. Inheritance is a little different.

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    Let's do some coding! Welshy's Avatar
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    Quote Originally Posted by homeyg
    Not quite. Inheritance is a little different.
    surely it's basic inheritance?

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    Ty all!

    Yes, that was just Psuedo-code, I figured as I was writing the thread I'd better come up with some code to demonstrate what I was think of doing

    Java is pretty class based, in Java I'd have done this differently. C++ seems more flexible though, to do this in Java I'd have written one or two clases with multiple methods to do what it seems I can do with structures in a dozen lines in C++.

    Anyways, I'm off to implement this and see how things work out

    Ty all again!

  13. #13
    C/C++ homeyg's Avatar
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    Quote Originally Posted by Welshy
    surely it's basic inheritance?
    Yes. But inheritance deals with classes and needs a special sytax. (I think it has a few hidden things that need attention like the behavior of the constructors in the classes).

  14. #14
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    Quote Originally Posted by Gatt9
    Ty all!
    ...to do this in Java I'd have written one or two clases with multiple methods to do what it seems I can do with structures in a dozen lines in C++.

    Anyways, I'm off to implement this and see how things work out

    Ty all again!
    <sigh>
    As someone posted, structures are for backwards compatibility with C. I thought you aspired to be a C++ programmer?

  15. #15
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    No that's not basic inheritance.
    Inheritance is inherting traits from a class to another class not having the class as a data member in you class.
    7stud I use structs all of the time. It's a good way to seperate things that have member functions etc. from things that just are data only. But as was said they do the exact same thing, so it is just a matter of preference.
    Last edited by prog-bman; 03-25-2005 at 10:30 PM.
    Woop?

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