C++ Math lrint()用法及代码示例

该函数使用当前舍入模式对给定值进行舍入，并返回 long int 类型的值。

用法

假设一个数字是 'x'。语法是：

long int lrint(data_type x);

参数

x: 可以是 float、double 或 long double 的值。

返回值

它返回 x 的舍入值，该值的返回类型为 long int。

例子1

让我们看一个简单的例子。

#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;
}

输出：

Enter the value which you want to round:7.8

Name of the methods are:
1. Rounding downwards
2. Rounding upwards
3. Rounding towards zero
4. Rounding to the nearest
Enter the number of rounding method:1

Rounding downwards,value is:7

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