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#ifndef LIFE_SRC_WORLD_H_
#define LIFE_SRC_WORLD_H_
#include <array>
#include <stack>
#include <tuple>
#include <cstdint>
#include "util/box_traverser.h"
namespace life {
template<
std::size_t WIDTH,
std::size_t HEIGHT
>
class World {
public:
static const std::size_t width = WIDTH;
static const std::size_t height = HEIGHT;
World():
area_(width, height) {
this->area_.for_each([&](std::size_t i, std::size_t j) {
this->matrix_[j][i] = false;
});
}
bool isLifeAt(std::ptrdiff_t x, std::ptrdiff_t y) const {
if ( this->area_(x, y) ) {
return this->matrix_[y][x];
} else {
return false; // end of world is dead
}
}
std::uint8_t lifeDensityAt(std::size_t x, std::size_t y) const {
std::uint8_t counter{};
counter += this->isLifeAt(x - 1, y);
counter += this->isLifeAt(x + 1, y);
counter += this->isLifeAt(x, y - 1);
counter += this->isLifeAt(x, y + 1);
counter += this->isLifeAt(x - 1, y + 1);
counter += this->isLifeAt(x - 1, y - 1);
counter += this->isLifeAt(x + 1, y + 1);
counter += this->isLifeAt(x + 1, y - 1);
return counter;
}
std::size_t getAge() const {
return this->age_;
}
std::size_t getPopulation() const {
return this->population_;
}
void summonLifeAt(std::size_t x, std::size_t y) {
if ( this->area_(x, y) ) {
if ( !this->matrix_[y][x] ) {
this->matrix_[y][x] = true;
this->population_ += 1;
}
}
}
void extinguishLifeAt(std::size_t x, std::size_t y) {
if ( this->area_(x, y) ) {
if ( this->matrix_[y][x] ) {
this->matrix_[y][x] = false;
this->population_ -= 1;
}
}
}
void tick() {
this->age_++;
std::stack<std::tuple<std::size_t, std::size_t, bool>> updates;
this->area_.for_each([&](std::size_t i, std::size_t j) {
const std::uint8_t d{this->lifeDensityAt(i, j)};
if ( this->matrix_[j][i] ) {
if ( d < 2 ) {
updates.emplace(i, j, false);
} else if ( d == 2 || d == 3 ) {
updates.emplace(i, j, true);
} else if ( d > 3 ) {
updates.emplace(i, j, false);
}
} else {
if ( d == 3 ) {
updates.emplace(i, j, true);
}
}
});
while ( !updates.empty() ) {
const auto& update = updates.top();
if ( std::get<2>(update) ) {
this->summonLifeAt(
std::get<0>(update),
std::get<1>(update)
);
} else {
this->extinguishLifeAt(
std::get<0>(update),
std::get<1>(update)
);
}
updates.pop();
}
}
private:
const util::BoxTraverser area_;
std::size_t age_{};
std::size_t population_{};
std::array<std::array<bool, WIDTH>, HEIGHT> matrix_;
};
}
#endif // LIFE_SRC_WORLD_H_
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