std::generate_canonical

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Numerics library

Common mathematical functions

Floating-point environment

Complex numbers

Numeric arrays

Pseudo-random number generation

Compile-time rational arithmetic (C++11)

Generic numeric operations

iota (C++11)

accumulate

inner_product

adjacent_difference

partial_sum

 

Pseudo-random number generation

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)

Generators

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

 

template< class RealType, size_t bits, class Generator > RealType generate_canonical( Generator& g );		(since C++11)

Generates a random floating point number in range [0; 1).

To generate enough entropy, calls g() exactly k times, where k = max(1, ⌈ b / log
2 R ⌉) and

• b = std::min<std::size_t>(bits, std::numeric_limits<RealType>::digits)
• R = g.max() - g.min() + 1.

Parameters

g

-

generator to use to acquire entropy

Return value

Floating point value in range [0; 1).

Exceptions

None except from those thrown by g

Notes

Some existing implementations have a bug where they may occasionally return 1.0 if RealType is float GCC #63176 LLVM #18767

Example

produce random numbers with 10 bits of randomness: this may produce only k*R distinct values

Run this code

#include <random>
#include <iostream>
 
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    for(int n=0; n<10; ++n) {
        std::cout << std::generate_canonical<double, 10>(gen) << ' ';
    }
}

Output:

0.208143 0.824147 0.0278604 0.343183 0.0173263 0.864057 0.647037 0.539467 0.0583497 0.609219

See also

uniform_real_distribution (C++11)

produces real values evenly distributed across a range (class template)