Thread: rand() in decimals.

  1. #1
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    rand() in decimals.

    Hi, I'm wondering how do I generate random numbers in decimals?
    Meaning between 0-1.

    Any ideas? rand() returns from the minimum of 1.

  2. #2
    C++ Witch laserlight's Avatar
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    Read Prelude's article on Using rand(), in particular about creating a uniform deviate.
    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

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    Thanks for the link, my mind must've slipped as this could also be done.

    Code:
           float k = (rand()%10);
           k = k/10;

  4. #4
    Code Goddess Prelude's Avatar
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    >float k = (rand()%10);
    >k = k/10;
    Apparently you didn't read the entire article. :P
    My best code is written with the delete key.

  5. #5
    Unregistered User Yarin's Avatar
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    I've always done it like so:
    Code:
    float frand(int chop, int perk = 10) {
       return (float(rand() % chop) * pow(10.0, float(perk))) / pow(10.0, float(perk));   }

  6. #6
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    Quote Originally Posted by Yarin View Post
    I've always done it like so:
    Code:
    float frand(int chop, int perk = 10) {
       return (float(rand() % chop) * pow(10.0, float(perk))) / pow(10.0, float(perk));   }
    You probably want to read (and understand) Prelude's page too - that is, if you care about the distribution of your random numbers. [And if you REALLY want good random numbers, don't use rand - as it's by no means guaranteed to be "good"].

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  7. #7
    Unregistered User Yarin's Avatar
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    I did read it quite a while ago, but I figured out that rand() was producing pretty much the same thing as her version of rand(). All I have to do is call srand() every 1k calls to rand().

  8. #8
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    Quote Originally Posted by Yarin View Post
    I did read it quite a while ago, but I figured out that rand() was producing pretty much the same thing as her version of rand(). All I have to do is call srand() every 1k calls to rand().
    Calling srand again after calling it the first time will NOT improve the distribution of your sequence - it will restart the sequence with a different seed, and depending on the seed value, it may give you the same sequence as last time or a different sequence. But it won't make the distribution any better.

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    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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