round() 用于 C++ 中的浮点数

round() for float in C++(round() 用于 C++ 中的浮点数)

问题描述

我需要一个简单的浮点舍入函数，因此:

I need a simple floating point rounding function, thus:

double round(double);

round(0.1) = 0
round(-0.1) = 0
round(-0.9) = -1

我可以在 math.h 中找到 ceil() 和 floor() - 但不能找到 round().

I can find ceil() and floor() in the math.h - but not round().

它是否以其他名称存在于标准 C++ 库中，或者是否缺失??

Is it present in the standard C++ library under another name, or is it missing??

推荐答案

从 C++11 开始在 cmath 中可用(根据 http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf)

It's available since C++11 in cmath (according to http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf)

#include <cmath>
#include <iostream>

int main(int argc, char** argv) {
  std::cout << "round(0.5):	" << round(0.5) << std::endl;
  std::cout << "round(-0.5):	" << round(-0.5) << std::endl;
  std::cout << "round(1.4):	" << round(1.4) << std::endl;
  std::cout << "round(-1.4):	" << round(-1.4) << std::endl;
  std::cout << "round(1.6):	" << round(1.6) << std::endl;
  std::cout << "round(-1.6):	" << round(-1.6) << std::endl;
  return 0;
}

输出:

round(0.5):  1
round(-0.5): -1
round(1.4):  1
round(-1.4): -1
round(1.6):  2
round(-1.6): -2

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