---
title: nearbyint
description: "基于当前的舍入方向，返回x的舍入值。"
url: https://www.hikunpeng.com/document/detail/zh/kunpengaccel/math-lib/devg-kml/kunpengaccel_kml_0242.html
sourcePath: /source/zh/kunpengaccel/math-lib/devg-kml/kunpengaccel_kml_0242.html
indexId: 2d828ff6be3db2abadc7e639c21dc952cc51841f47f67cc5cd54bf5224a59a6468
---
# nearbyint

基于当前的舍入方向，返回x的舍入值。

#### 接口定义

C interface：

float nearbyintf(float x);

double nearbyint(double x);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在nearbyintf中，x是单精度浮点类型。 在nearbyint中，x是双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |


#### 返回值

- 返回x的舍入值，x ∈ (-inf, inf)。
- 输入+0，返回+0。
- 输入-0，返回-0。
- 输入±∞，返回±∞。
- 输入nan，返回nan。


#### 依赖

C: "km.h"


#### 示例

C interface：```
// typical usage
    double x1 = 0.0, x2 = -0.0, x3 = 1.5, x4 = -2.5;
    // special handing
    double a = INFINITY, b = -INFINITY, c = NAN;
    // pnearbyint result
    printf("nearbyint(0.0) = %.15f\n", nearbyint(x1));
    printf("nearbyint(-0.0) = %.15f\n", nearbyint(x2));
    printf("nearbyint(1.5) = %.15f\n", nearbyint(x3));
    printf("nearbyint(-2.5) = %.15f\n", nearbyint(x4));
    printf("nearbyint(INFINITY) = %.15f\n", nearbyint(a));
    printf("nearbyint(-INFINITY) = %.15f\n", nearbyint(b));
    printf("nearbyint(NAN) = %.15f\n", nearbyint(c));
    /* 
     * nearbyint(0.0) = 0.000000000000000
     * nearbyint(-0.0) = -0.000000000000000
     * nearbyint(1.5) = 2.000000000000000
     * nearbyint(-2.5) = -2.000000000000000
     * nearbyint(INFINITY) = inf
     * nearbyint(-INFINITY) = -inf
     * nearbyint(NAN) = nan
     * */
```