Random generator 0 1

This is a discussion on Random generator 0 1 within the C Programming forums, part of the General Programming Boards category; Hi I'd like to write a random number generator between 0 and1. I'm doing like that: Code: #include<stdio.h> #include <stdlib.h> ...

  1. #1
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    Random generator 0 1

    Hi

    I'd like to write a random number generator between 0 and1.
    I'm doing like that:

    Code:
    #include<stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int main(){
    int b;
    float r;
    
    srand(time(NULL));
    
    printf("%d",RAND_MAX);
    
    for (b=11;b>0;b--){
    
            r=rand();
    
            printf("%f\n", r/RAND_MAX);
    
            }
    return 0;
    }
    but i get this output:

    Code:
    21474836470.216477
    0.471353
    0.312465
    0.644094
    0.796645
    0.112260
    0.999378
    0.374815
    0.463826
    0.021919
    0.175329
    why the first one is not normalized?

    Thanks

    D.

  2. #2
    C++ Witch laserlight's Avatar
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    You printed RAND_MAX without a newline, so you confused that and the very first pseudorandom number printed. Try:
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int main(){
        int b;
        float r;
    
        srand(time(NULL));
    
        printf("%d\n", RAND_MAX);
    
        for (b=11;b>0;b--){
            r = rand();
    
            printf("%f\n", r/RAND_MAX);
        }
        return 0;
    }
    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
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    many thanks, I made an easy error.

    D.

  4. #4
    C++ Witch laserlight's Avatar
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    By the way, the range you get is [0.0, 1.0], but [0.0, 1.0) is more commonly used, methinks. If you want the latter, you would have to say, add 1.0 to RAND_MAX in the divisor.
    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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