# skipList

[**@twine-protocol/twine-core v0.1.0**](https://docs.twine.world/twine-js/twine-protocol/twine-core/index) • **Docs**

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[twine-js](https://docs.twine.world/twine-js/index) / [@twine-protocol/twine-core](https://docs.twine.world/twine-js/twine-protocol/twine-core/index) / skipList

## Function: skipList()

> **skipList**(`radix`, `fromIndex`, `toIndex`, `byLink`): `Generator`<`number`, `void`, `unknown`>

Get an iterator of indices that can be used to skip through the chain.

This can either provide the pulse indices themselves or a list of array indices of the links list for each pulse along the path.

This will not include the from/to indices themselves.

A radix of 1 doesn't make sense since `1^r` is always `1`.

A radix of 0 is interpreted as no radix skipping, so the list just has the previous pulse cid, therefore a radix 0 skiplist is just a decreasing list of pulse indices.

### Parameters

| Parameter   | Type      | Default value | Description                                                       |
| ----------- | --------- | ------------- | ----------------------------------------------------------------- |
| `radix`     | `number`  | `undefined`   | The radix used for the chain                                      |
| `fromIndex` | `number`  | `undefined`   | The higher index                                                  |
| `toIndex`   | `number`  | `undefined`   | The lower index                                                   |
| `byLink`    | `boolean` | `false`       | If true, will return the list of array indices for the links list |

### Returns

`Generator`<`number`, `void`, `unknown`>

### Example

```js
const radix = 10
const fromIndex = 23
const toIndex = 5
const actual = Array.from(skipList(radix, fromIndex, toIndex))
// actual == [ 20, 10, 9, 8, 7, 6 ]
// because... 23 is in the `n * 10^1` range so it's links list should have `[22, 20]`
// same deal for 20 which has links `[19, 10]` so we can skip to 10
// then we get to the `n * 10^0` range and we can skip to 9, 8, 7, 6

// The array indices for this correspond to jumps of
// `10^1`, `10^1`, `10^0`, `10^0`, `10^0`, `10^0`
// so the array indices would be `[1, 1, 0, 0, 0, 0]`

Array.from(skipList(10, 23, 5, true)) // == [ 1, 1, 0, 0, 0, 0 ]
```

### Defined in

[packages/twine-core/src/links.ts:81](https://github.com/twine-protocol/twine-js/blob/3800995f9c83f4f5711bcf3062ea754a1e4448ce/packages/twine-core/src/links.ts#L81)