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 / log 2 R ⌉) and

• 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