std::generate_canonical

Generates a random floating point number in range [ ​0​ ,  1 )

To generate enough entropy, generate_canonical() will call g() exactly \(\small k\) k times, where \(\small k = \max(1, \lceil \frac{b}{\log_2 R} \rceil)\) k = max(1, ⌈ b / log2 R ⌉)

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

Parameters

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 MSVC STL #1074. This is LWG issue 2524

Example

#include <iostream>
#include <random>
 
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) << ' ';
    std::cout << '\n';
}

0.208143 0.824147 0.0278604 0.343183 0.0173263 0.864057 0.647037 0.539467 0.0583497 0.609219

See also