# Grid traversal functions

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

## gridDisk

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDisk(H3Index origin, int k, H3Index* out);`

`h3.grid_disk(origin, k)`

`List<Long> gridDisk(long origin, int k);`

List<String> gridDisk(String origin, int k);

`h3.gridDisk(origin, k)`

gridDisk produces indices within k distance of the origin index.

gridDisk was previously named *k-ring* after the concept of a ring with
distance k. 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 as zero, which can happen when crossing a pentagon.

## maxGridDiskSize

- C
- Python
- Java
- JavaScript (Live)

`H3Error maxGridDiskSize(int k, int64_t *out);`

This function exists for memory management and is not exposed.

This function exists for memory management and is not exposed.

This function exists for memory management and is not exposed.

Maximum number of indices that result from the `gridDisk`

algorithm with the given `k`

.

## gridDiskDistances

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDiskDistances(H3Index origin, int k, H3Index* out, int* distances);`

`h3.grid_disk_distances(origin, k)`

`List<List<Long>> gridDiskDistances(long origin, int k);`

List<List<String>> gridDiskDistances(String origin, int k);

`h3.gridDiskDistances(origin, k)`

gridDiskDistances 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 as zero, which can happen when crossing a pentagon.

## gridDiskUnsafe

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDiskUnsafe(H3Index origin, int k, H3Index* out);`

`h3.grid_disk_unsafe(h, k)`

`List<List<Long>> gridDiskUnsafe(Long h3, int k) throws PentagonEncounteredException;`

List<List<String>> gridDiskUnsafe(String h3Address, int k) throws PentagonEncounteredException;

This function is not exposed.

`gridDiskUnsafe`

produces indexes within `k`

distance of the origin index.
The function returns an error code when one of the returned by this
function is a pentagon or is in the pentagon distortion area. In this case,
the output behavior of the `out`

array is undefined.

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 provided array must be of size `maxGridDiskSize(k)`

.

Returns 0 (`E_SUCCESS`

) if no pentagonal distortion is encountered.

## gridDiskDistancesUnsafe

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDiskDistancesUnsafe(H3Index origin, int k, H3Index* out, int* distances);`

`h3.grid_disk_distances_unsafe(h, k)`

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

This function is not exposed.

`gridDiskDistancesUnsafe`

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. The provided array must be of size `maxGridDiskSize(k)`

.

Returns 0 (`E_SUCCESS`

) if no pentagonal distortion is encountered.

## gridDiskDistancesSafe

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDiskDistancesSafe(H3Index origin, int k, H3Index* out, int* distances);`

`h3.grid_disk_distances_safe(h, k)`

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

This function is not exposed.

`gridDiskDistancesSafe`

produces indexes 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 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. The provided array must be of size `maxGridDiskSize(k)`

.

Returns 0 (`E_SUCCESS`

) on success.

## gridDisksUnsafe

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDisksUnsafe(H3Index* h3Set, int length, int k, H3Index* out);`

`h3.grid_disks_unsafe(h, k)`

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

This function is not exposed.

`gridDisksUnsafe`

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

Returns 0 (`E_SUCCESS`

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

## gridRingUnsafe

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridRingUnsafe(H3Index origin, int k, H3Index* out);`

`h3.grid_ring_unsafe(h, k)`

`List<Long> gridRingUnsafe(long h3, int k) throws PentagonEncounteredException;`

List<String> gridRingUnsafe(String h3Address, int k) throws PentagonEncounteredException;

`h3.gridRingUnsafe(h3Index, k)`

Produces the hollow hexagonal ring centered at origin with sides of length k.

Returns 0 (`E_SUCCESS`

) if no pentagonal distortion was encountered.

## gridPathCells

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridPathCells(H3Index start, H3Index end, H3Index* out);`

`h3.grid_path_cells(start, end)`

`List<Long> gridPathCells(long start, long end) throws LineUndefinedException`

List<String> gridPathCells(String startAddress, String endAddress) throws LineUndefinedException

`h3.gridPathCells(start, end)`

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.

## gridPathCellsSize

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridPathCellsSize(H3Index start, H3Index end, int64_t* size);`

This function exists for memory management and is not exposed.

This function exists for memory management and is not exposed.

This function exists for memory management and is not exposed.

Number of indexes in a line from the start index to the end index, to be used for allocating memory.

Returns 0 (`E_SUCCESS`

) on success, or an error if the line cannot be computed.

## gridDistance

- C
- Python
- Java
- JavaScript (Live)

`H3Error gridDistance(H3Index origin, H3Index h3, int64_t *distance);`

`h3.grid_distance(h1, h2)`

`long gridDistance(long a, long b) throws DistanceUndefinedException;`

long gridDistance(String a, String b) throws DistanceUndefinedException;

`h3.gridDistance(a, b)`

Provides the distance in grid cells between the two indexes.

Returns 0 (`E_SUCCESS`

) on success, or an error 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.

## cellToLocalIj

- C
- Python
- Java
- JavaScript (Live)

`H3Error cellToLocalIj(H3Index origin, H3Index h3, uint32_t mode, CoordIJ *out);`

`h3.cell_to_local_ij(origin, h)`

`CoordIJ cellToLocalIj(long origin, long h3) throws PentagonEncounteredException, LocalIjUndefinedException;`

CoordIJ cellToLocalIj(String originAddress, String h3Address) throws PentagonEncounteredException, LocalIjUndefinedException;

`h3.cellToLocalIj(origin, h3)`

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

`mode`

is reserved for future expansion and must be set to `0`

.

This function's output is not guaranteed to be compatible across different versions of H3.

## localIjToCell

- C
- Python
- Java
- JavaScript (Live)

`H3Error localIjToCell(H3Index origin, const CoordIJ *ij, uint32_t mode, H3Index *out);`

`h3.local_ij_to_cell(origin, i, j)`

`long localIjToCell(long origin, CoordIJ ij) throws LocalIjUndefinedException;`

String localIjToCell(String originAddress, CoordIJ ij) throws LocalIjUndefinedException;

`h3.localIjToCell(origin, coords)`

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

`mode`

is reserved for future expansion and must be set to `0`

.

This function's output is not guaranteed to be compatible across different versions of H3.