std::uniform_real_distribution

C++

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Named requirements

Language support library

Concepts library (C++20)

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Technical Specifications

Numerics library

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Floating-point environment (C++11)

Complex numbers

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Compile-time rational arithmetic (C++11)

Numeric algorithms

gcd (C++17)

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Generic numeric operations

iota (C++11)

accumulate

inner_product

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reduce (C++17)

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inclusive_scan (C++17)

exclusive_scan (C++17)

transform_inclusive_scan (C++17)

transform_exclusive_scan (C++17)

Bit operations

bit_cast (C++20)

ispow2 (C++20)

ceil2 (C++20)

floor2 (C++20)

log2p1 (C++20)

Pseudo-random number generation

Uniform random bit generators

UniformRandomBitGenerator (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

std::uniform_real_distribution

Member functions

uniform_real_distribution::uniform_real_distribution

uniform_real_distribution::reset

Generation

uniform_real_distribution::operator()

Characteristics

uniform_real_distribution::auniform_real_distribution::b

uniform_real_distribution::param

uniform_real_distribution::min

uniform_real_distribution::max

Non-member functions

operator==operator!=

operator<<operator>>

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

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

P(i|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	RealType
param_type	the type of the parameter set, see RandomNumberDistribution.

Member functions

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

Non-member functions

operator==operator!=	compares two distribution objects (function)
operator<<operator>>	performs stream input and output on pseudo-random number distribution (function template)

Notes

To create a distribution over the closed interval [a,b], std::nextafter(b, std::numeric_limits<RealType>::max()) may be used as the second parameter.

Some existing implementations have a bug where they may occasionally return b if RealType is float GCC #63176 LLVM #18767. This is caused by LWG issue 2524

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)
        std::cout << dis(gen) << ' '; //Each call to dis(gen) generates a new random double
    }
    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