8000 Add docs for h3Distance by isaacbrodsky · Pull Request #101 · uber/h3 · GitHub
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Add docs for h3Distance #101

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Jul 30, 2018
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Add docs for h3Distance #101

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13 changes: 13 additions & 0 deletions docs/api/distance.md
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# Distance functions

## h3Distance

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

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
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Is it worth outlining the meaning of the different error codes here?

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h3Distance itself only returns -1 on any kind of error right now, it doesn't preserve the more specific error code from h3ToIjk

indexes are not comparable (different resolutions), too far apart, or are separated by pentagonal
distortion.
12 changes: 7 additions & 5 deletions examples/distance.c
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Expand Up @@ -14,8 +14,8 @@
* limitations under the License.
*/
/**
* Example program that calculates the distance in kilometers between two
* hexagon indices.
* Example program that calculates the distance in hexagons and in kilometers
* between two hexagon indices.
*/

// mean Earth radius
Expand Down Expand Up @@ -59,12 +59,14 @@ int main(int argc, char *argv[]) {
printf(
5E3C "origin: (%lf, %lf)\n"
"destination: (%lf, %lf)\n"
"distance: %lfkm\n",
"grid distance: %d\n"
"distance in km: %lfkm\n",
radsToDegs(geoHQ1.lat), radsToDegs(geoHQ1.lon), radsToDegs(geoHQ2.lat),
radsToDegs(geoHQ2.lon),
radsToDegs(geoHQ2.lon), h3Distance(h3HQ1, h3HQ2),
haversineDistance(geoHQ1.lat, geoHQ1.lon, geoHQ2.lat, geoHQ2.lon));
// Output:
// origin: (37.775236, 237.580245)
// destination: (37.789991, 237.597879)
// distance: 2.256850km
// grid distance: 2340
// distance in km: 2.256850km
}
0