std::uniform_real_distribution

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

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

P(x|a,b) = 1 b - a

.

std::uniform_real_distribution satisfies all requirements of RandomNumberDistribution

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.

Member types

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

Member functions

(constructor) (C++11)	constructs new distribution (public member function)
reset (C++11)	resets the internal state of the distribution (public member function)
Generation
operator() (C++11)	generates the next random number in the distribution (public member function)
Characteristics
ab	returns the distribution parameters (public member function)
param (C++11)	gets or sets the distribution parameter object (public member function)
min (C++11)	returns the minimum potentially generated value (public member function)
max (C++11)	returns the maximum potentially generated value (public member function)

Non-member functions

operator==operator!= (C++11)(C++11)(removed in C++20)	compares two distribution objects (function)
operator<<operator>> (C++11)	performs stream input and output on pseudo-random number distribution (function template)

Notes

It is difficult to create a distribution over the closed interval $\small[a, b]$ $[a, b]$ 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 $\small b$ $b$ (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.

Example

print 10 random numbers between 1 and 2

Run this code

#include <random>
#include <iostream>
 
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

Compiler support
Freestanding and hosted
Language
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Technical specifications
Symbols index
External libraries

Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Floating-point environment (C++11)
Complex numbers
Numeric arrays
Pseudo-random number generation
Factor operations
gcd (C++17)
lcm (C++17)
Interpolations
midpoint (C++20)
lerp (C++20)
Generic numeric operations
iota (C++11)
ranges::iota (C++23)
accumulate
inner_product
adjacent_difference
partial_sum
reduce (C++17)
transform_reduce (C++17)
inclusive_scan (C++17)
exclusive_scan (C++17)
transform_inclusive_scan (C++17)
transform_exclusive_scan (C++17)
Bit operations
bit_cast (C++20)
byteswap (C++23)
has_single_bit (C++20)
bit_ceil (C++20)
bit_floor (C++20)
bit_width (C++20)
rotl (C++20)
rotr (C++20)
countl_zero (C++20)
countl_one (C++20)
countr_zero (C++20)
countr_one (C++20)
popcount (C++20)
endian (C++20)

Uniform random bit generators
uniform_random_bit_generator (C++20)
Engines and engine adaptors
linear_congruential_engine (C++11)
mersenne_twister_engine (C++11)
subtract_with_carry_engine (C++11)
discard_block_engine (C++11)
independent_bits_engine (C++11)
shuffle_order_engine (C++11)
Non-deterministic generator
random_device (C++11)
Distributions
Uniform distributions
uniform_int_distribution (C++11)
uniform_real_distribution (C++11)
generate_canonical (C++11)
Bernoulli distributions
bernoulli_distribution (C++11)
binomial_distribution (C++11)
negative_binomial_distribution (C++11)
geometric_distribution (C++11)
Poisson distributions
poisson_distribution (C++11)
exponential_distribution (C++11)
gamma_distribution (C++11)
weibull_distribution (C++11)
extreme_value_distribution (C++11)
Normal distributions
normal_distribution (C++11)
lognormal_distribution (C++11)
chi_squared_distribution (C++11)
cauchy_distribution (C++11)
fisher_f_distribution (C++11)
student_t_distribution (C++11)
Sampling distributions
discrete_distribution (C++11)
piecewise_constant_distribution (C++11)
piecewise_linear_distribution (C++11)
Seed Sequences
seed_seq (C++11)
C library
rand
srand
RAND_MAX

Member functions
uniform_real_distribution::uniform_real_distribution (C++11)
uniform_real_distribution::reset (C++11)
Generation
uniform_real_distribution::operator() (C++11)
Characteristics
uniform_real_distribution::auniform_real_distribution::b (C++11)(C++11)
uniform_real_distribution::param (C++11)
uniform_real_distribution::min (C++11)
uniform_real_distribution::max (C++11)
Non-member functions
operator==operator!= (C++11)(C++11)(until C++20)
operator<<operator>> (C++11)(C++11)