相关疑难解决方法(0)

任何人都可以解释我从这个简单的程序使用的输出std::map.请注意,我插入p到地图中,但还q没有说它发现它们两者,但也说地图中只有1个元素!

#include <map>
#include <iostream>

struct screenPoint {
  float x = 0, y = 0;
  screenPoint(float x_, float y_): x{x_}, y{y_}{}
};

bool operator<(const screenPoint& left, const screenPoint& right){
  return left.x<right.x&&left.y<right.y;
}

std::map<screenPoint, float> positions;

int main(int argc, const char * argv[]) {

  auto p = screenPoint(1,2);
  auto q = screenPoint(2,1);
  positions.emplace(p,3);

  auto f = positions.find(p);
  auto g = positions.find(q);

  if (f == positions.end()){
    std::cout << "f not found";
  } else {
    std::cout << …