// Warning Warning Warning
// This shows how bad random number result,
// if you re-seed your generator
// g++ -std=c++0x main_badrandom.cpp 
#include <iostream>
#include <fstream>
#include <ctime>
#include <random>
#include <iomanip>
using namespace std;

std::mt19937 gener; // define generator

double bad_unirand(void){
  static uniform_real_distribution<double> unif_dist(0,1); 
  return (unif_dist(gener));
}

int main(){  
  ofstream outunif("badunif");
  outunif << std::fixed<<std::setprecision(30); // 30 decimal output
  gener.seed(static_cast<uint_fast32_t> (std::time(0))); // seed for the generator
  cout<<"Bad uniform distribution to file badunif \n";
  for(int i = 0; i < 100000; i++) {
    // re-seed generator after every 10000 numbers
    if(i%10000==0) {gener.seed(static_cast<uint_fast32_t> (std::time(0)));};
    outunif  << bad_unirand() << "\n";
  }
  outunif.close();
  cout<<"If you look at the contents of file badunif, you probably find nothing wrong\n";
  cout<<"Now plot the data.\nFor example in gnuplot, type\n plot 'badunif' w d\n";
  cout<<"See the non-randomness?\n";  
  return 0;
}