---
title: significand
description: "以浮点形式返回x的有效数字。"
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sourcePath: /source/zh/kunpengboostkithistory/240RC2/accel/kunpengaccel_kml_16_0569.html
indexId: cfe81dde9a3ec1115928e83ec060136f505437691c70cc84ee49edc93b216dc176
---
# significand

以浮点形式返回x的有效数字。

#### 接口定义

C interface：

float significandf(float x);

double significand(double x);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在significandf中，x是单精度浮点类型。 在significand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的有效数字，|y| ∈ [1, 2)。
- 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, x5 = 0x1p-1024;
// special handing
double a = INFINITY, b = -INFINITY, c = NAN;
// print result
printf("significand(0.0) = %.15f\n", significand(x1));
printf("significand(-0.0) = %.15f\n", significand(x2));
printf("significand(1.5) = %.15f\n", significand(x3));
printf("significand(-2.5) = %.15f\n", significand(x4));
printf("significand(0x1p-1024) = %.15f\n", significand(x5));
printf("significand(INFINITY) = %.15f\n", significand(a));
printf("significand(-INFINITY) = %.15f\n", significand(b));
printf("significand(NAN) = %.15f\n", significand(c));
/*
* significand(0.0) = 0.000000000000000
* significand(-0.0) = -0.000000000000000
* significand(1.5) = 1.500000000000000
* significand(-2.5) = -1.250000000000000
* significand(0x1p-1024) = 1.000000000000000
* significand(INFINITY) = inf
* significand(-INFINITY) = -inf
* significand(NAN) = nan
*
* */
```