17.29 and 17.30

[MRamez]

Hi,
In random_gen functions, e and ud are static. Because they are static, they will be initialized only once. This means their range and seed cannot be changed after the first call to random_gen. For example:
random_gen(0, 1, 9);
random_gen(3, 0, 100);
The second call to random_gen returns a random unsigned from [1, 9] and the seed that e uses is 0.
This is my proposed solution for 17.30 (the same can be applied to 17.29):

template <unsigned seed, unsigned max, unsigned min>
unsigned random_gen()
{
   static std::default_random_engine e(seed);
   static std::uniform_int_distribution<unsigned> ud(min, max);
   return ud(e);
}

Thanks