about #include files and header files

This is a discussion on about #include files and header files within the C++ Programming forums, part of the General Programming Boards category; I am wanting to generate a random number from inside a member function of a class thats located in its ...

  1. #1
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    about #include files and header files

    I am wanting to generate a random number from inside a member function of a class thats located in its header file.

    My question is..where do I put the #include <time.h> and the needed variables to use it (by it I mean the variables the tutorial thats on this site about 'generating random numbers' uses)?

    Do I put #include <time.h>, <cstdlib>, time_t seconds,time(&seconds) and srand((unsigned int) seconds) in the header file or do I put them in the main.cpp?

  2. #2
    i dont know Vicious's Avatar
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    If my class needs a certain header, I include that header in the class's header file. It makes the code feel more complete.
    What is C++?

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    and the Hat of Guessing tabstop's Avatar
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    The headers must appear in the file where the code calling rand() and srand() and time() will be.

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    >> The headers must appear in the file where the code calling rand() and srand() and time() will be.

    I prefer this solution over the one Vicious proposes. In most cases, you'll be calling those functions in the cpp file, so #include the headers for those functions in your cpp file. Adding the #includes to your header just forces people using your class to #include them as well, which defeats part of the purpose of separating header and source files.

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    Quote Originally Posted by Daved View Post
    >> The headers must appear in the file where the code calling rand() and srand() and time() will be.

    I prefer this solution over the one Vicious proposes. In most cases, you'll be calling those functions in the cpp file, so #include the headers for those functions in your cpp file. Adding the #includes to your header just forces people using your class to #include them as well, which defeats part of the purpose of separating header and source files.
    Yes, this goes along the same lines as encapsulation & scope. If a certain piece of code doesn't need access to other code, then don't give it access.

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    do I have to put

    time_t seconds;
    time(&seconds);
    srand((unsigned int) seconds);

    in each member function of my class that uses rand()?

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    No. That code should be run only once for the entire time your program is running. Some people do it at the beginning of main, but you can place wherever is appropriate to ensure it is called once before you ever call rand().

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    i dont know Vicious's Avatar
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    Just to be sure I even understand what I am talking about:

    If you need to declare a time_t variable in the header including the time header before the class header in your cpp file will work? I suppose I should try this again, as my only memories of this is the compiler complaining about "time_t" not being a type.

    Sorry about that mislead!
    What is C++?

  9. #9
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    Quote Originally Posted by Vicious View Post
    Just to be sure I even understand what I am talking about:

    If you need to declare a time_t variable in the header including the time header before the class header in your cpp file will work? I suppose I should try this again, as my only memories of this is the compiler complaining about "time_t" not being a type.

    Sorry about that mislead!
    If you need time_t in your header, include <ctime> in your header because anyone that uses your header will need to include <ctime> anyways, otherwise if you don't need any types or functions from <ctime> in your header, just include it in your .cpp file.
    You should never organize your code so that it depends on the order of #include statements...

  10. #10
    i dont know Vicious's Avatar
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    Ok, that's what I was thinking when I made my original post. I was just making sure I wasn't totally off.
    What is C++?

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