random/randomize

This is a discussion on random/randomize within the C Programming forums, part of the General Programming Boards category; Hey, I'm studying for my exams. I was testing a program from my course, but it doesn't seem to work. ...

  1. #1
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    random/randomize

    Hey,

    I'm studying for my exams. I was testing a program from my course, but it doesn't seem to work. I was using the functions randomize() and random(100)+1. According to our teacher, these prototypes should be declared in <stdlib.h>. I included this header-file, but the compiler keeps giving an error:missing prototype for randomize, missing prototype for random. Can anyone help me asap please? I've been staring myself blind on this problem.

    Thanks,
    Lynn

  2. #2
    ZuK
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    Wrong language. I remember pascal had the functions randomize() and random().
    in C they are called srand() and rand().
    Kurt

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    Thank you very much for your help, the program does work now. I found in a FAQ that you have to use the time-function. I used it and it worked, but I don't understand what it does. Would you mind explaining that to me?

    Thanks,
    Lynn

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    Quote Originally Posted by Lynn
    Thank you very much for your help, the program does work now. I found in a FAQ that you have to use the time-function. I used it and it worked, but I don't understand what it does. Would you mind explaining that to me?

    Thanks,
    Lynn
    Would anyone care to explain this to me?

  5. #5
    Just Lurking Dave_Sinkula's Avatar
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    time returns a value that will be different at least every second, which makes it an easy first choice to seed the random number generator.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  6. #6
    ZuK
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    rand basically produces only one sequence of numbers. That means it calculates the new result from the result of the previous run. By calling srand you actually just set the starting point in this sequence. By using the current system-time to seed the function you will get a different sequence each time you run your program.
    But you should use google to find out more about pseudo random generators. I'm shure there are much better explanations on the net.
    Kurt

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    dwk

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