---
title: catan
description: "计算复数x的反正切值。"
url: https://www.hikunpeng.com/document/detail/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0274.html
sourcePath: /source/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0274.html
indexId: af2c08653f659b2eeab843fb422ebc062634c296f6ea1a9253661f3323c7a2bc61
---
# catan

计算复数x的反正切值。

#### 接口定义

C interface：

float complex catanf(float complex x);

double complex catan(double complex x);

long double complex catanl(long double complex x);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在catanf中，x是复数单精度浮点类型。 在catan中，x是复数双精度浮点类型。 在catanl中，x是复数长双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |


#### 返回值

- 返回x的反正切结果y。
- 特殊值说明如下所示。| 输入值实部（x.real） | 输入值虚部（x.imag） | 输出值实部（y.real） | 输出值虚部（y.imag） |
| --- | --- | --- | --- |
| \-inf | \-inf | \-pi/2 | \-0.0 |
| \-inf | < +0.0 | \-pi/2 | \-0.0 |
| \-inf | \-0.0 | \-pi/2 | \-0.0 |
| \-inf | +0.0 | \-pi/2 | +0.0 |
| \-inf | > +0.0 | \-pi/2 | +0.0 |
| \-inf | inf | \-pi/2 | +0.0 |
| \-inf | \-nan | \-pi/2 | +0.0 |
| \-inf | nan | \-pi/2 | +0.0 |
| < +0.0 | \-inf | \-pi/2 | \-0.0 |
| < +0.0 | inf | \-pi/2 | +0.0 |
| < +0.0 | \-nan | nan | nan |
| < +0.0 | nan | nan | nan |
| \-0.0 | \-inf | \-pi/2 | \-0.0 |
| \-0.0 | \-0.0 | \-0.0 | \-0.0 |
| \-0.0 | +0.0 | \-0.0 | 0.0 |
| \-0.0 | inf | \-pi/2 | +0.0 |
| \-0.0 | \-nan | nan | nan |
| \-0.0 | nan | nan | nan |
| +0.0 | \-inf | pi/2 | \-0.0 |
| +0.0 | \-0.0 | +0.0 | \-0.0 |
| +0.0 | +0.0 | +0.0 | +0.0 |
| +0.0 | inf | pi/2 | +0.0 |
| +0.0 | \-nan | nan | nan |
| +0.0 | nan | nan | nan |
| > +0.0 | \-inf | pi/2 | \-0.0 |
| > +0.0 | inf | pi/2 | +0.0 |
| > +0.0 | \-nan | nan | nan |
| > +0.0 | nan | nan | nan |
| inf | \-inf | pi/2 | \-0.0 |
| inf | < +0.0 | pi/2 | \-0.0 |
| inf | \-0.0 | pi/2 | \-0.0 |
| inf | +0.0 | pi/2 | +0.0 |
| inf | > +0.0 | pi/2 | +0.0 |
| inf | inf | pi/2 | +0.0 |
| inf | \-nan | pi/2 | +0.0 |
| inf | nan | pi/2 | +0.0 |
| \-nan | \-inf | nan | \-0.0 |
| \-nan | < +0.0 | nan | nan |
| \-nan | \-0.0 | nan | \-0.0 |
| \-nan | +0.0 | nan | +0.0 |
| \-nan | > +0.0 | nan | nan |
| \-nan | inf | nan | +0.0 |
| \-nan | \-nan | nan | nan |
| \-nan | nan | nan | nan |
| nan | \-inf | nan | \-0.0 |
| nan | < +0.0 | nan | nan |
| nan | \-0.0 | nan | \-0.0 |
| nan | +0.0 | nan | +0.0 |
| nan | > +0.0 | nan | nan |
| nan | inf | nan | +0.0 |
| nan | \-nan | nan | nan |
| nan | nan | nan | nan |


#### 依赖

C: "km.h"


#### 示例

C interface：```
// typical usage
    double x1 = 1.0, x2 = 2.0, x3 = 3.0, x4 = 4.0;
    double complex cx1 = __builtin_complex(x1, x2);
    double complex cx2 = __builtin_complex(x3, x4);
    double complex cx3 = __builtin_complex(NAN, NAN);
    double complex cx4 = __builtin_complex(INFINITY, -INFINITY);
    double ry;
    double iy;
    ry = __real__ catan(cx1);
    iy = __imag__ catan(cx1);
    printf("catan(cx1) = %.15f, %.15f\n", ry, iy);
    ry = __real__ catan(cx2);
    iy = __imag__ catan(cx2);
    printf("catan(cx2) = %.15f, %.15f\n", ry, iy);
    ry = __real__ catan(cx3);
    iy = __imag__ catan(cx3);
    printf("catan(cx3) = %.15f, %.15f\n", ry, iy);
    ry = __real__ catan(cx4);
    iy = __imag__ catan(cx4);
    printf("catan(cx4) = %.15f, %.15f\n", ry, iy);

result:
   /*
    * catan(cx1) = 1.338972522294493, 0.402359478108525
    * catan(cx2) = 1.448306995231464, 0.158997191679999
    * catan(cx3) = nan, nan
    * catan(cx4) = 1.570796326794897, -0.000000000000000
    */
```