cppdraft_translate/cppdraft/rand/req/urng.md

[rand.req.urng]

29 Numerics library [numerics]

29.5 Random number generation [rand]

29.5.3 Requirements [rand.req]

29.5.3.3 Uniform random bit generator requirements [rand.req.urng]

1

#

A uniform random bit generatorg of type G is a function object returning unsigned integer values such that each value in the range of possible results has (ideally) equal probability of being returned.

[Note 1:

The degree to which g's results approximate the ideal is often determined statistically.

— end note]

templateconcept uniform_random_bit_generator =invocable<G&> && unsigned_integral<invoke_result_t<G&>> &&requires {{ G::min() } -> same_as<invoke_result_t<G&>>; { G::max() } -> same_as<invoke_result_t<G&>>; requires bool_constant<(G::min() < G::max())>::value; };

2

#

Let g be an object of type G.

G modelsuniform_random_bit_generator only if

• (2.1)

G​::​min() <= g(),

• (2.2)

g() <= G​::​max(), and

• (2.3)

g() has amortized constant complexity.

3

#

A class G meets the uniform random bit generator requirements ifG models uniform_random_bit_generator,invoke_result_t<G&> is an unsigned integer type ([basic.fundamental]), andG provides a nested typedef-name result_type that denotes the same type as invoke_result_t<G&>.