< cpp‎ | numeric‎ | random
Defined in header <random>
template< class RealType = double >
class uniform_real_distribution;
(since C++11)

Produces random floating-point values x, uniformly distributed on the interval [a, b), that is, distributed according to the probability density function:

P(x|a,b) =
b − a

std::uniform_real_distribution satisfies all requirements of RandomNumberDistribution.


[edit] Template parameters

RealType - The result type generated by the generator. The effect is undefined if this is not one of float, double, or long double.

[edit] Member types

Member type Definition
result_type(C++11) RealType
param_type (C++11) the type of the parameter set, see RandomNumberDistribution.

[edit] Member functions

constructs new distribution
(public member function) [edit]
resets the internal state of the distribution
(public member function) [edit]
generates the next random number in the distribution
(public member function) [edit]
returns the distribution parameters
(public member function) [edit]
gets or sets the distribution parameter object
(public member function) [edit]
returns the minimum potentially generated value
(public member function) [edit]
returns the maximum potentially generated value
(public member function) [edit]

[edit] Non-member functions

(C++11)(C++11)(removed in C++20)
compares two distribution objects
(function) [edit]
performs stream input and output on pseudo-random number distribution
(function template) [edit]

[edit] Notes

It is difficult to create a distribution over the closed interval [a, b] from this distribution. Using std::nextafter(b, std::numeric_limits<RealType>::max()) as the second parameter does not always work due to rounding error.

Most existing implementations have a bug where they may occasionally return b (GCC #63176 LLVM #18767 MSVC STL #1074). This was originally only thought to happen when RealType is float and when LWG issue 2524 is present, but it has since been shown that neither is required to trigger the bug.

[edit] Example

Print 10 random numbers between 1 and 2.

#include <iostream>
#include <random>
int main()
    std::random_device rd;  // Will be used to obtain a seed for the random number engine
    std::mt19937 gen(rd()); // Standard mersenne_twister_engine seeded with rd()
    std::uniform_real_distribution<> dis(1.0, 2.0);
    for (int n = 0; n < 10; ++n)
        // Use dis to transform the random unsigned int generated by gen into a 
        // double in [1, 2). Each call to dis(gen) generates a new random double.
        std::cout << dis(gen) << ' ';
    std::cout << '\n';

Possible output:

1.80829 1.15391 1.18483 1.38969 1.36094 1.0648 1.97798 1.27984 1.68261 1.57326

[edit] External links

Drawing random floating-point numbers from an interval — © 2022. Frédéric Goualard, Université de Nantes.