---
title: annuity
description: "计算年金现值系数，输入参数为实数。"
url: https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/240RC2/accel/kunpengaccel_kml_16_0601.html
sourcePath: /source/zh/kunpengboostkithistory/240RC2/accel/kunpengaccel_kml_16_0601.html
indexId: 51732975521d2e1b6afd2337b1e0b6ed670674392346ae1aae20210c4d7c3f1376
---
# annuity

计算年金现值系数，输入参数为实数。

#### 接口定义

C interface：

float annuityf(float x, float y);

double annuity(double x, double y);


#### 参数

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


#### 返回值

- x大于-1且y ∈(-∞, +∞)，返回计算结果。
- 输入x为任意值，y为±0，返回0。
- 输入x为nan，y为任意值，返回nan。
- 输入x为任意值，y为nan，返回nan。
- 输入x为+∞，y为-1，则返回-1；y < -1，则返回-∞；y ∈(-1, 0)，则返回-0。
- 输入x为0，y != 0，则返回y。
- 输入x为-1，y < 0，则返回-1；y > 0，则返回+∞。
- 输入x < -1，y != 0，则返回nan。
- 输入y为-∞，x ∈(-1， 0)，则返回1.0 / x；x > 0，则返回-∞。
- 输入y为+∞，x ∈(-1， 0)，则返回+∞；x > 0，则返回1.0 / x。


#### 依赖

C: "km.h"


#### 示例

C interface：
```
// print result
printf("annuity(1.0, 10.0) = %.15f\n", annuity(1.0, 10.0));
printf("annuity(0.5, -3.0) = %.15f\n", annuity(0.5, -3.0));
printf("annuity(0.3, -10.0) = %.15f\n", annuity(1.0, 10.0));
printf("annuity(4, 2.0) = %.15f\n", annuity(0.5, -3.0));
printf("annuity(INFINITY, 0) = %.15f\n", annuity(INFINITY, 0));
printf("annuity(INFINITY, 0) = %.15f\n", annuity(INFINITY, 0));
printf("annuity(1.0, NAN) = %.15f\n", annuity(1.0, NAN));
printf("annuity(NAN, 1.0) = %.15f\n", annuity(NAN, 1.0));
printf("annuity(INFINITY, -1.0) = %.15f\n", annuity(INFINITY, -1.0));
printf("annuity(INFINITY, -10.0) = %.15f\n", annuity(INFINITY, -10.0));
printf("annuity(INFINITY, 10.0) = %.15f\n", annuity(INFINITY, 10.0));
printf("annuity(0, 1.0) = %.15f\n", annuity(0, 1.0));
printf("annuity(-1.0, -1.0) = %.15f\n", annuity(-1.0, -1.0));
printf("annuity(-1.0, 1.0) = %.15f\n", annuity(-1.0, 1.0));
printf("annuity(-10.0, 1.0) = %.15f\n", annuity(-10.0, 1.0));
printf("annuity(-0.5, -INFINITY) = %.15f\n", annuity(-0.5, -INFINITY));
printf("annuity(0.5, -INFINITY) = %.15f\n", annuity(0.5, -INFINITY));
printf("annuity(-0.5, INFINITY) = %.15f\n", annuity(-0.5, INFINITY));
printf("annuity(0.5, INFINITY) = %.15f\n", annuity(0.5, INFINITY));
/*
* annuity(1.0, 10.0) = 0.999023437500000
* annuity(0.5, -3.0) = -4.750000000000000
* annuity(0.3, -10.0) = 0.999023437500000
* annuity(4, 2.0) = -4.750000000000000
* annuity(INFINITY, 0) = 0.000000000000000
* annuity(INFINITY, 0) = 0.000000000000000
* annuity(1.0, NAN) = nan
* annuity(NAN, 1.0) = nan
* annuity(INFINITY, -1.0) = -1.000000000000000
* annuity(INFINITY, -10.0) = -inf
* annuity(INFINITY, 10.0) = 0.000000000000000
* annuity(0, 1.0) = 1.000000000000000
* annuity(-1.0, -1.0) = -1.000000000000000
* annuity(-1.0, 1.0) = inf
* annuity(-10.0, 1.0) = nan
* annuity(-0.5, -INFINITY) = -2.000000000000000
* annuity(0.5, -INFINITY) = -inf
* annuity(-0.5, INFINITY) = inf
* annuity(0.5, INFINITY) = 2.000000000000000
*
* */
```