Random number between zero and one in c++

Question

i want to create a random number between 0 and 1 but my codes output is zero.

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main()
{
  srand(time(0));

  for(int x=0;x<100;x++)
  {
      cout<<(rand()%10)/10<<endl;
  }
  return 0;
}

I recommend you use [modern C++ random number facilities](http://en.cppreference.com/w/cpp/numeric/random/uniform_real_distribution) instead of `rand()`. — Fred Larson, Jan 31 '17 at 15:19
See http://stackoverflow.com/questions/686353/c-random-float-number-generation — jhilmer, Jan 31 '17 at 15:21

Jesper Juhl · Accepted Answer · 2017-01-31T15:40:47.673

This: (rand()%10)/10 gives you a (low quality) random integer between zero and RAND_MAX, then you use modulo to turn that into a (biased) integer between zero and nine, then you perform integer division by 10 which will always be a value less than 1 which will be truncated to zero.

A much better solution would be to use the random facilities from C++11 and use a std::uniform_real_distribution to obtain your value between 0 and 1.

score 0 · Answer 2 · answered Jan 31 '17 at 15:18

0

You are dividing an int. Anything lower than one will be cut to 0. You need to declare/cast a double or float (to have decimals).

answered Jan 31 '17 at 15:18

Carele

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No - even casting to float or double won't give you an uniform distributed random number between 0 and 1 – jhilmer Jan 31 '17 at 15:24
1

@jhilmer I only answered part of the question (why the output is 0). Actually there is not actual question to begin with so i did just give him a hint to try and correct his code. I should have added that this is not the solution to the whole problem. – Carele Jan 31 '17 at 15:30

Random number between zero and one in c++

2 Answers2