Math.cpp

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#include "Math.h"
#include "Constants.h"
#include <array>
 
using namespace Eule;
 
// Checks if the random number generator is initialized. Does nothing if it is, initializes if it isn't.
#define MAKE_SURE_RNG_IS_INITIALIZED if (!isRngInitialized) InitRng();
 
void Math::InitRng()
{
    // Create truly random source (from hardware events)
    std::random_device randomSource;
 
    // Generate enough truly random values to populate the entire state of the mersenne twister
    std::array<int, std::mt19937::state_size> seedValues;
    std::generate_n(seedValues.data(), seedValues.size(), std::ref(randomSource));
    std::seed_seq seedSequence(seedValues.begin(), seedValues.end());
 
    // Seed the mersenne twister with these values
    rng = std::mt19937(seedSequence);
 
    isRngInitialized = true;
 
    return;
}
 
// Will return a random double between 0 and 1
double Math::Random()
{
    MAKE_SURE_RNG_IS_INITIALIZED;
 
    return (rng() % 694206942069ll) / 694206942069.0;
}
 
// Will return a random unsigned integer.
unsigned int Math::RandomUint()
{
    MAKE_SURE_RNG_IS_INITIALIZED;
 
    return rng();
}
 
// Will return a random integer
unsigned int Math::RandomInt()
{
    MAKE_SURE_RNG_IS_INITIALIZED;
 
    // Since this is supposed to return a random value anyways,
    // we can let the random uint overflow without any problems.
    return (int)rng();
}
 
// Will return a random double within a range  
// These bounds are INCLUSIVE!
double Math::RandomRange(double min, double max)
{
    return (Random() * (max - min)) + min;
}
 
// Will return a random integer within a range. This is faster than '(int)RandomRange(x,y)'
// These bounds are INCLUSIVE!
int Math::RandomIntRange(int min, int max)
{
    return (rng() % (max + 1 - min)) + min;
}
 
double Math::Oscillate(const double a, const double b, const double counter, const double speed)
{
    return (sin(counter * speed * PI - HALF_PI) * 0.5 + 0.5) * (b-a) + a;
}
 
bool Math::RandomChance(const double chance)
{
    return Random() <= chance;
}
 
std::mt19937 Math::rng;
bool Math::isRngInitialized = true;