Getting integer random values instead of real values using boost::random library

Question

I am trying to get real random values using boost::random libraries. This is my code:

#include <iostream>

#include <boost/random/uniform_real_distribution.hpp>
#include <boost/random/mersenne_twister.hpp>

boost::random::mt19937 eng = boost::random::mt19937();
boost::random::uniform_real_distribution<double> urd =
   boost::random::uniform_real_distribution<double>(0,20);

for (int i = 0; i <= 100; i++)
   std::cout << urd(eng) << std::endl;

But I get integer numbers between 0 and 20.

How can I do?

I also tried another engine:

#include <iostream>

#include <boost/random/uniform_real_distribution.hpp>
#include <boost/random/lagged_fibonacci.hpp>

boost::random::lagged_fibonacci607 eng = boost::random::lagged_fibonacci607();
boost::random::uniform_real_distribution<double> urd =
   boost::random::uniform_real_distribution<double>(0,20);

for (int i = 0; i <= 100; i++)
   std::cout << urd(eng) << std::endl;

But nothing... (always integer values)

What do you mean by nothing? Do you get no output or unexpected/unintended output? — , Jul 09 '12 at 23:33
Your example code works perfectly for me. 2.50366 6.34199 15.275 19.0044 9.81178 0.688922 13.2722 8.77489 2.51793 7.63117 4.20418 15.3103 ... — David Schwartz, Jul 10 '12 at 00:28

Jesse Good · Accepted Answer · 2012-07-10T00:54:27.600

How about setting the precision before you output? std::cout.precision(15);?

Or use:

std::cout.precision(std::numeric_limits<double>::digits10);

Example

#include <iostream>
#include <limits>
#include <boost/random/uniform_real_distribution.hpp>
#include <boost/random/mersenne_twister.hpp>

int main()
{
    boost::random::mt19937 eng = boost::random::mt19937();
    boost::random::uniform_real_distribution<double> urd =
    boost::random::uniform_real_distribution<double>(0,20);

    std::cout.precision(std::numeric_limits<double>::digits10);
    for (int i = 0; i <= 100; i++)
    {
       std::cout << urd(eng) << std::endl;
    }
}

The default precision for std::cout is set at 6, so it should work without setting this, but...

@Andry: Please try out the example I posted. – Jesse Good Jul 09 '12 at 23:41 — Jesse Good, Jul 09 '12 at 23:41

Getting integer random values instead of real values using boost::random library

1 Answers1