std::generate_canonical - cppreference.com (original) (raw)

| | | | | ----------------------------------------------------------------------------------------------------------------------------------------- | | ------------- | | template< class RealType, std::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, 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 ⌉) and

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

[edit] Parameters

g	-	generator to use to acquire entropy

[edit] Return value

Floating point value in range [0, 1).

[edit] Exceptions

None except from those thrown by g.

[edit] 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.

[edit] Example

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

Possible output: