---
id: traversal
title: Grid traversal functions
sidebar_label: Traversal
slug: /api/traversal
---

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';

Grid traversal allows finding cells in the vicinity of an origin cell, and determining how to traverse the grid from one cell to another.

## kRing

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
void kRing(H3Index origin, int k, H3Index* out);
```

</TabItem>
<TabItem value="python">

```py
h3.k_ring(origin, k)
```

</TabItem>
<TabItem value="java">

```java
List<Long> kRing(long origin, int k);
List<String> kRing(String origin, int k);
```

</TabItem>
<TabItem value="javascript">

```js
h3.kRing(origin, k)
```

```js live
function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.kRing(h, k);
}
```

</TabItem>
</Tabs>

k-rings produces indices within k distance of the origin index.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and
all neighboring indices, and so on.

Output is placed in the provided array in no particular order. Elements of
the output array may be left zero, as can happen when crossing a pentagon.

## maxKringSize

<Tabs
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  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int maxKringSize(int k);
```

</TabItem>
<TabItem value="python">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
<TabItem value="java">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
<TabItem value="javascript">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
</Tabs>

Maximum number of indices that result from the kRing algorithm with the given k.

## kRingDistances

<Tabs
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  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
void kRingDistances(H3Index origin, int k, H3Index* out, int* distances);
```

</TabItem>
<TabItem value="python">

```py
h3.k_ring_distances(origin, k)
```

</TabItem>
<TabItem value="java">

```java
List<List<Long>> kRingDistances(long origin, int k);
List<List<String>> kRingDistances(String origin, int k);
```

</TabItem>
<TabItem value="javascript">

```js
h3.kRingDistances(origin, k)
```

```js live
function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.kRingDistances(h, k);
}
```

</TabItem>
</Tabs>

k-rings produces indices within k distance of the origin index.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and
all neighboring indices, and so on.

Output is placed in the provided array in no particular order. Elements of
the output array may be left zero, as can happen when crossing a pentagon.

## hexRange

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int hexRange(H3Index origin, int k, H3Index* out);
```

</TabItem>
<TabItem value="python">

```py
h3.hex_range(h, k)
```

</TabItem>
<TabItem value="java">

```java
List<List<Long>> hexRange(Long h3, int k) throws PentagonEncounteredException;
List<List<String>> hexRange(String h3Address, int k) throws PentagonEncounteredException;
```

</TabItem>
<TabItem value="javascript">

:::note

This function is not exposed.

:::

</TabItem>
</Tabs>

hexRange produces indexes within k distance of the origin index.
Output behavior is undefined when one of the indexes returned by this
function is a pentagon or is in the pentagon distortion area.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and
all neighboring indexes, and so on.

Output is placed in the provided array in order of increasing distance from
the origin.

Returns 0 if no pentagonal distortion is encountered.
 
## hexRangeDistances

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  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int hexRangeDistances(H3Index origin, int k, H3Index* out, int* distances);
```

</TabItem>
<TabItem value="python">

```py
h3.hex_range_distances(h, k)
```

</TabItem>
<TabItem value="java">

:::note

This function is not exposed because the same functionality is exposed by `hexRange`

:::

</TabItem>
<TabItem value="javascript">

:::note

This function is not exposed.

:::

</TabItem>
</Tabs>

hexRange produces indexes within k distance of the origin index.
Output behavior is undefined when one of the indexes returned by this
function is a pentagon or is in the pentagon distortion area.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and
all neighboring indexes, and so on.

Output is placed in the provided array in order of increasing distance from
the origin. The distances in hexagons is placed in the distances array at
the same offset.
 
Returns 0 if no pentagonal distortion is encountered.

## hexRanges

<Tabs
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  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int hexRanges(H3Index* h3Set, int length, int k, H3Index* out);
```

</TabItem>
<TabItem value="python">

```py
h3.hex_ranges(h, k)
```

</TabItem>
<TabItem value="java">

:::note

This function is not exposed because the same functionality is exposed by `hexRange`

:::

</TabItem>
<TabItem value="javascript">

:::note

This function is not exposed.

:::

</TabItem>
</Tabs>

hexRanges takes an array of input hex IDs and a max k-ring and returns an
array of hexagon IDs sorted first by the original hex IDs and then by the
k-ring (0 to max), with no guaranteed sorting within each k-ring group.

Returns 0 if no pentagonal distortion was encountered. Otherwise, output
is undefined

## hexRing

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int hexRing(H3Index origin, int k, H3Index* out);
```

</TabItem>
<TabItem value="python">

```py
h3.hex_ring(h, k)
```

</TabItem>
<TabItem value="java">

```java
List<Long> hexRing(long h3, int k) throws PentagonEncounteredException;
List<String> hexRing(String h3Address, int k) throws PentagonEncounteredException;
```

</TabItem>
<TabItem value="javascript">

```js
h3.hexRing(h3Index, k)
```

```js live
function example() {
  const h = '85283473fffffff';
  const k = 1;
  return h3.hexRing(h, k);
}
```

</TabItem>
</Tabs>

Produces the hollow hexagonal ring centered at origin with sides of length k.
 
Returns 0 if no pentagonal distortion was encountered.

## h3Line

<Tabs
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  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int h3Line(H3Index start, H3Index end, H3Index* out);
```

</TabItem>
<TabItem value="python">

```py
h3.h3_line(start, end)
```

</TabItem>
<TabItem value="java">

```java
List<Long> h3Line(long start, long end) throws LineUndefinedException
List<String> h3Line(String startAddress, String endAddress) throws LineUndefinedException
```

</TabItem>
<TabItem value="javascript">

```js
h3.h3Line(start, end)
```

```js live
function example() {
  const start = '85283473fffffff';
  const end = '8528342bfffffff';
  return h3.h3Line(start, end);
}
```

</TabItem>
</Tabs>

Given two H3 indexes, return the line of indexes between them (inclusive).

This function may fail to find the line between two indexes, for
example if they are very far apart. It may also fail when finding
distances for indexes on opposite sides of a pentagon.

*Notes:*

 * The specific output of this function should not be considered stable
   across library versions. The only guarantees the library provides are
   that the line length will be `h3Distance(start, end) + 1` and that
   every index in the line will be a neighbor of the preceding index.

 * Lines are drawn in grid space, and may not correspond exactly to either
   Cartesian lines or great arcs.

## h3LineSize

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int h3LineSize(H3Index start, H3Index end);
```

</TabItem>
<TabItem value="python">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
<TabItem value="java">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
<TabItem value="javascript">

:::note

This function exists for memory management and is not exposed.

:::

</TabItem>
</Tabs>

Number of indexes in a line from the start index to the end index,
to be used for allocating memory. Returns a negative number if the
line cannot be computed.

## h3Distance

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int h3Distance(H3Index origin, H3Index h3);
```

</TabItem>
<TabItem value="python">

```py
h3.h3_distance(h1, h2)
```

</TabItem>
<TabItem value="java">

```java
int h3Distance(long a, long b) throws DistanceUndefinedException;
int h3Distance(String a, String b) throws DistanceUndefinedException;
```

</TabItem>
<TabItem value="javascript">

```js
h3.h3Distance(a, b)
```

```js live
function example() {
  const start = '85283473fffffff';
  const end = '8528342bfffffff';
  return h3.h3Distance(start, end);
}
```

</TabItem>
</Tabs>

Returns the distance in grid cells between the two indexes.

Returns a negative number if finding the distance failed. Finding the distance can fail because the two
indexes are not comparable (different resolutions), too far apart, or are separated by pentagonal
distortion. This is the same set of limitations as the local IJ coordinate space functions.

## experimentalH3ToLocalIj

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int experimentalH3ToLocalIj(H3Index origin, H3Index h3, CoordIJ *out);
```

</TabItem>
<TabItem value="python">

```py
h3.experimental_h3_to_local_ij(origin, h)
```

</TabItem>
<TabItem value="java">

```java
CoordIJ experimentalH3ToLocalIj(long origin, long h3) throws PentagonEncounteredException, LocalIjUndefinedException;
CoordIJ experimentalH3ToLocalIj(String originAddress, String h3Address) throws PentagonEncounteredException, LocalIjUndefinedException;
```

</TabItem>
<TabItem value="javascript">

```js
h3.experimentalH3ToLocalIj(origin, h3)
```

```js live
function example() {
  const origin = '85283473fffffff';
  const h = '8528342bfffffff';
  const {i, j} = h3.experimentalH3ToLocalIj(origin, h);
  return [i, j];
}
```

</TabItem>
</Tabs>

Produces local IJ coordinates for an H3 index anchored by an origin.

This function is experimental, and its output is not guaranteed
to be compatible across different versions of H3.

## experimentalLocalIjToH3

<Tabs
  groupId="language"
  defaultValue="c"
  values={[
    {label: 'C', value: 'c'},
    {label: 'Python', value: 'python'},
    {label: 'Java', value: 'java'},
    {label: 'JavaScript (Live)', value: 'javascript'},
  ]
}>
<TabItem value="c">

```c
int experimentalLocalIjToH3(H3Index origin, const CoordIJ *ij, H3Index *out);
```

</TabItem>
<TabItem value="python">

```py
h3.experimental_local_ij_to_h3(origin, i, j)
```

</TabItem>
<TabItem value="java">

```java
long experimentalLocalIjToH3(long origin, CoordIJ ij) throws LocalIjUndefinedException;
String experimentalLocalIjToH3(String originAddress, CoordIJ ij) throws LocalIjUndefinedException;
```

</TabItem>
<TabItem value="javascript">

```js
h3.experimentalLocalIjToH3(origin, coords)
```

```js live
function example() {
  const h = '85283473fffffff';
  const coords = {i: 0, j: 0};
  return h3.experimentalLocalIjToH3(h, coords);
}
```

</TabItem>
</Tabs>

Produces an H3 index from local IJ coordinates anchored by an origin.

This function is experimental, and its output is not guaranteed
to be compatible across different versions of H3.
