C++ Reference: Standard C++ Library reference: C Library: cmath: round

C++官网参考链接：https://cplusplus.com/reference/cmath/round/

函数 
<cmath>
round
C99
double round(double x);      
float roundf(float x);
long double roundl(long double x);
C++11
double round(double x);      
float round(float x);
long double round(long double x);     
double round (T x);   // additional overloads for integral types

向最近舍入 
返回最接近x的整数值，中间情况舍入到远离0。
C99
头文件提供了该函数的泛型类型的宏版本。 
C++11
在此头文件（）中为整型（