lrint(x)函数详解

long int lrint(data_type x);

#include <iostream>  
#include<math.h>  
#include <cfenv>  
using namespace std;  
int main()  
{  
    float r;  
    int str;  
    cout<<"Enter the value which you want to round :";  
    std::cin >> r ;  
    cout<<'\n';  
    cout<<"Name of the methods are :"<<'\n'<<"1. Rounding downwards"<<'\n'<<"2. Rounding upwards"<<'\n'<<"3.   
    Rounding towards zero"<<'\n'<<"4. Rounding to the nearest"<<'\n';  
    cout<<"Enter the number of rounding method :";  
    cin>>str;  
    cout<<'\n';  
    switch(str)  
    {  
        case 1:  
        fesetround(FE_DOWNWARD);  
        cout<<"Rounding downwards,value is :"<<lrint(r)<<'\n';  
        break;  
        case 2:  
        fesetround(FE_UPWARD);  
        cout<<"Rounding upwards,value is :"<<lrint(r)<<'\n';  
        break;  
        case 3:  
        fesetround(FE_TOWARDZERO);  
        cout<<"Rounding towards zero,value is :"<<lrint(r)<<'\n';  
        break;  
        case 4:  
        fesetround(FE_TONEAREST);  
        cout<<"Rounding to nearest,value is :"<<lrint(r)<<'\n';  
        break;  
        default:  
        cout<<"wrong method";  
    }  
       return 0;  
}