---
title: Gamma function
id: 5a23c84252665b21eecc7e76
challengeType: 5
videoUrl: ''
localeTitle: 伽玛功能
---
## Description
实现一个算法（或更多）来计算Gamma （$ \ Gamma $）函数（仅在实际字段中）。 Gamma功能可以定义为： $ \ Gamma（x）= \ displaystyle \ int_0 ^ \ infty t ^ {x-1} e ^ { - t} dt $
## Instructions
## Tests
```yml
tests:
- text: gamma应该是一个功能。
testString: assert(typeof gamma=='function')
- text: 'gamma("+tests[0]+")应该返回一个数字。'
testString: assert(typeof gamma(.1)=='number')
- text: 'gamma("+tests[0]+")应该返回"+results[0]+" 。'
testString: assert.equal(round(gamma(.1)), round(9.513507698668736))
- text: 'gamma("+tests[1]+")应该返回"+results[1]+" 。'
testString: assert.equal(round(gamma(.2)), round(4.590843711998803))
- text: 'gamma("+tests[2]+")应该返回"+results[2]+" 。'
testString: assert.equal(round(gamma(.3)), round(2.9915689876875904))
- text: 'gamma("+tests[3]+")应该返回"+results[3]+" 。'
testString: assert.equal(round(gamma(.4)), round(2.218159543757687))
- text: 'gamma("+tests[4]+")应返回"+results[4]+" 。'
testString: assert.equal(round(gamma(.5)), round(1.7724538509055159))
```
## Challenge Seed
```js
function gamma (x) {
// Good luck!
}
```
### After Test
```js
console.info('after the test');
```
## Solution
```js
// solution required
```