#include <stdio.h> /* printf() */
#include <stdlib.h> /* rand(), srand(), RAND_MAX */
#include <time.h> /* time() */
 
double randd(double min, double max) {
    int r = rand();
    double delta = max - min; /* assume max > min */
    double tmp = r / (RAND_MAX + 1.0); /* generate up to but excluding max */
    return tmp * delta + min;
}
 
int main(void) {
    srand(time(0));
    printf("%f\n", randd(4.2, 4.3));
    printf("%f\n", randd(0.0001, 0.0000001));
    printf("%f\n", randd(-0.1, 0.1));
    printf("%f\n", randd(2.7182, 3.1415));
    return 0;
}
 

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