std::random_device is not a member of std

Question

The random_device class is not recognized as part of the std:: namespace until I include <bits/stdc++.h>.

I want to ask you if there is another solution for this, because I don't really want to include all standard libraries for this purpose.

std::random_device rd;
std::mt19937 gen(rd()); 
std::uniform_int_distribution<> dis(1,5); 
std::cout<<dis(gen);

[**Don't** include ``](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h) — Some programmer dude, Oct 26 '20 at 13:46
Note that generally, you will get an answer for this kind of questions on the site *cppreference*: [cppreference::std::random_device](https://en.cppreference.com/w/cpp/numeric/random/random_device) — Damien, Oct 26 '20 at 13:56

Adrian Mole · Accepted Answer · 2020-10-26T14:51:08.650

It is a good sign, indeed, that you don't want to include all the Standard Library header files (via the appalling and non-standard #include <bits/stdc++.h> concoction)! However, you do need to (explicitly) include the headers relevant to the aspects/components of the Standard Library that you actually use.

In the case of the std::random_device class (and, also, the other two random-related classes that you use), you will need to include the header that defines those classes, with the following line:

#include <random>

Also, for the std::cout (and related) classes, you will need #include <iostream>.

As mentioned in the comments, the cppreference website is as good a place as any to get a quick guide to which header(s) you need to include for any of the std::xxxx classes, although you will soon 'get to know' the relevant headers for the more common Standard Library classes.

std::random_device is not a member of std

1 Answers1