rngthing.h

#include <random>
 
using RandomGen = std::mt19937;
extern RandomGen g_RandomNumberGenerator;
 
void
seed_lua_prng();
 
inline auto
random_up_to(RandomGen& rng, int limit) -> int
{
    RandomGen::result_type res = rng();
    // Cutting off the incomplete [0,n) chunk at the max value makes the result
    // more evenly distributed. -Kyz
    RandomGen::result_type up_to_max =
      RandomGen::max() - (RandomGen::max() % limit);
    while (res > up_to_max) {
        res = rng();
    }
 
    return static_cast<int>(res % limit);
}
 
inline auto
random_up_to(int limit) -> int
{
    return random_up_to(g_RandomNumberGenerator, limit);
}
 
inline auto
RandomFloat() -> float
{
    return static_cast<float>(g_RandomNumberGenerator() / 4294967296.0);
}
 
inline auto
RandomFloat(float fLow, float fHigh) -> float
{
    // SCALE() but l1 = 0 and h1 = 1 so simplifies to this
    return (RandomFloat() * (fHigh - fLow)) + fLow;
}
 
inline auto
RandomInt(int low, int high) -> int
{
    return random_up_to(g_RandomNumberGenerator, high - low + 1) + low;
}
 
inline auto
RandomInt(int n) -> int
{
    return random_up_to(g_RandomNumberGenerator, n);
}
 
inline auto
RandomInt(RandomGen& rng, int n) -> int
{
    return random_up_to(rng, n);
}
 
 
inline auto
randomf(const float low = -1.F, const float high = 1.F) -> float
{
    return RandomFloat(low, high);
}