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/*
* RNG.h, part of VCMI engine
*
* Authors: listed in file AUTHORS in main folder
*
* License: GNU General Public License v2.0 or later
* Full text of license available in license.txt file, in main folder
*
*/
#pragma once
VCMI_LIB_NAMESPACE_BEGIN
namespace vstd
{
class DLL_LINKAGE RNG
{
public:
virtual ~RNG() = default;
/// Returns random number in range [lower, upper]
virtual int nextInt(int lower, int upper) = 0;
/// Returns random number in range [lower, upper]
virtual int64_t nextInt64(int64_t lower, int64_t upper) = 0;
/// Returns random number in range [lower, upper]
virtual double nextDouble(double lower, double upper) = 0;
/// Returns random number in range [0, upper]
virtual int nextInt(int upper) = 0;
/// Returns random number in range [0, upper]
virtual int64_t nextInt64(int64_t upper) = 0;
/// Returns random number in range [0, upper]
virtual double nextDouble(double upper) = 0;
/// Generates an integer between 0 and the maximum value it can hold.
/// Should be only used for seeding other generators
virtual int nextInt() = 0;
/// Returns integer using binomial distribution
/// returned value is number of successfull coin flips with chance 'coinChance' out of 'coinsCount' attempts
virtual int nextBinomialInt(int coinsCount, double coinChance) = 0;
};
}
namespace RandomGeneratorUtil
{
template<typename Container>
auto nextItem(const Container & container, vstd::RNG & rand) -> decltype(std::begin(container))
{
if(container.empty())
throw std::runtime_error("Unable to select random item from empty container!");
return std::next(container.begin(), rand.nextInt64(0, container.size() - 1));
}
template<typename Container>
auto nextItem(Container & container, vstd::RNG & rand) -> decltype(std::begin(container))
{
if(container.empty())
throw std::runtime_error("Unable to select random item from empty container!");
return std::next(container.begin(), rand.nextInt64(0, container.size() - 1));
}
template<typename Container>
size_t nextItemWeighted(Container & container, vstd::RNG & rand)
{
assert(!container.empty());
int64_t totalWeight = std::accumulate(container.begin(), container.end(), 0);
assert(totalWeight > 0);
int64_t roll = rand.nextInt64(0, totalWeight - 1);
for (size_t i = 0; i < container.size(); ++i)
{
int chance = container[i];
if(roll < chance)
return i;
roll -= chance;
}
return container.size() - 1;
}
template<typename Container>
void randomShuffle(Container & container, vstd::RNG & rand)
{
int64_t n = std::distance(container.begin(), container.end());
for(int64_t i = n - 1; i > 0; --i)
{
auto randIndex = rand.nextInt64(0, i);
std::swap(*(container.begin() + i), *(container.begin() + randIndex));
}
}
}
VCMI_LIB_NAMESPACE_END
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