generating random double between x and y??

[jasonkk]

Hi ! I'm just so confused with how to generate the random double ranging between 'lower' and upper. My code is out of the range I set up. Please let me know which part should be fixed! thank you

  
int = lower, upper;
cin>> lower >> upper;
srand(time(NULL));
double rand_number2 = (rand() / (double)RAND_MAX * upper) + lower; 

[dutch]

If you must use rand() then maybe something like this:

    double r = (rand() / (double)RAND_MAX) * (upper - lower) + lower;

Or using the C++ random library.

std::default_random_engine rnd{std::random_device{}()};
std::uniform_real_distribution<double> dist(lower, upper);

double r = dist(rnd);

[George P]

Line 2 is invalid. int lower, upper;

[jasonkk]

Thank you guys!!