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#facebook-immutable で階乗計算
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#facebook-immutable で階乗計算 | |
facebook-immutable で階乗計算 | |
##Range() | |
http://facebook.github.io/immutable-js/docs/#/Range | |
>Returns a IndexedSeq of numbers from `start` (inclusive) to `end` (exclusive), by `step`, where `start` defaults to 0, `step` to 1, and `end` to infinity. When `start` is equal to `end`, returns empty range. | |
>Range(start?: number, end?: number, step?: number): IndexedSeq<number> | |
```js | |
Range() // [0,1,2,3,...] | |
Range(10) // [10,11,12,13,...] | |
Range(10,15) // [10,11,12,13,14] | |
Range(10,30,5) // [10,15,20,25] | |
Range(30,10,5) // [30,25,20,15] | |
Range(30,30,5) // [] | |
``` | |
##コード | |
```js | |
var _ = require('immutable'); | |
var plus = function(a, b) | |
{ | |
return a * b; | |
}; | |
``` | |
階乗を求める関数 | |
```js | |
var factorial = function(n) | |
{ | |
var x = _.Range(1, n + 1) // natural numbers starts from 1 to n | |
.reduce(plus); | |
return x; | |
}; | |
``` | |
または、 | |
```js | |
var factorial = function(n) | |
{ | |
var x = _.Range(1); // natural numbers starts from 1 | |
.take(n) | |
.reduce(plus); | |
return x; | |
}; | |
``` | |
表示 | |
```js | |
console.log(factorial(3)); // 1*2*3 = 6 | |
``` |
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