std::uniform_int_distribution

 

C++

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Feature test macros (C++20)

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Numerics library

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gcd (C++17)	lcm (C++17)
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add_sat (C++26) sub_sat (C++26) saturate_cast (C++26)	mul_sat (C++26) div_sat (C++26)
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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)
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has_single_bit (C++20)     bit_cast (C++20) bit_ceil (C++20) bit_floor (C++20) bit_width (C++20) rotl (C++20) rotr (C++20)	popcount (C++20) countl_zero (C++20) countl_one (C++20) countr_zero (C++20) countr_one (C++20) byteswap (C++23) endian (C++20)

 

Pseudo-random number generation

Uniform random bit generators   uniform_random_bit_generator (C++20) Random number engines linear_congruential_engine (C++11) mersenne_twister_engine (C++11) subtract_with_carry_engine (C++11) philox_engine (C++26) Random number engine adaptors discard_block_engine (C++11) independent_bits_engine (C++11) shuffle_order_engine (C++11) Predefined random number generators Non-deterministic random numbers random_device (C++11) Utilities generate_canonical (C++11) seed_seq (C++11) Random number algorithms ranges::generate_random (C++26) C random library rand    srand    RAND_MAX

Random number 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)

 

std::uniform_int_distribution

Member functions

uniform_int_distribution::uniform_int_distribution

uniform_int_distribution::reset

Generation

uniform_int_distribution::operator()

Characteristics

uniform_int_distribution::auniform_int_distribution::b

uniform_int_distribution::param

uniform_int_distribution::min

uniform_int_distribution::max

Non-member functions

operator==operator!= (C++11)(C++11)(until C++20)

operator<<operator>> (C++11)(C++11)

 

Defined in header <random>
template< class IntType = int > class uniform_int_distribution;		(since C++11)

Produces random integer values \(\small i\)i, uniformly distributed on the closed interval \(\small[a, b]\)[a, b], that is, distributed according to the discrete probability function

\({\small P(i|a,b) =}\frac{1}{b - a + 1}\)P(i|a,b) =

1

b − a + 1

.

std::uniform_int_distribution satisfies all requirements of RandomNumberDistribution.

Template parameters

IntType

-

The result type generated by the generator. The effect is undefined if this is not one of short, int, long, long long, unsigned short, unsigned int, unsigned long, or unsigned long long.

Member types

Member type	Definition
result_type (C++11)	IntType
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 (C++11)	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)

Example

This program simulates throwing 6-sided dice.

Run this code

#include <iostream>
#include <random>
 
int main()
{
    std::random_device rd;  // a seed source for the random number engine
    std::mt19937 gen(rd()); // mersenne_twister_engine seeded with rd()
    std::uniform_int_distribution<> distrib(1, 6);
 
    // Use distrib to transform the random unsigned int
    // generated by gen into an int in [1, 6]
    for (int n = 0; n != 10; ++n)
        std::cout << distrib(gen) << ' ';
    std::cout << '\n';
}

Possible output:

1 1 6 5 2 2 5 5 6 2