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feat: add haversineDistance #80

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Merged
merged 3 commits into from
Sep 5, 2024
Merged

feat: add haversineDistance #80

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0b223a1
feat: add `haversineDistance`
vil02 Aug 31, 2024
5067bdb
style: avoid `return`
vil02 Sep 2, 2024
470d5bb
style: rename to `isClose`
vil02 Sep 2, 2024
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53 changes: 53 additions & 0 deletions maths/haversine_distance.nim
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Original file line number Diff line number Diff line change
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# Haversine formula

import std/math

func haversineDistance(latitudeA, longitudeA, latitudeB,
longitudeB: float): float =
## returns the length of the shortest path connecting the input points on an unit sphere.
## The input points are represented by their spherical/geographical coordinates.
## The inputs are expected to be in radians.
let
dLatitude = latitudeB - latitudeA
dLongitude = longitudeB - longitudeA
a = sin(dLatitude / 2.0)^2 + cos(latitudeA) * cos(latitudeB) * sin(
dLongitude / 2.0)^2
2.0 * arcsin(sqrt(a))

when isMainModule:
import std/[unittest, sequtils, strformat]
suite "haversineDistance":
const testCases = [
(0.0, 0.0, 0.0, 0.0, 0.0),
(0.0, 0.0, PI / 2.0, 0.0, PI / 2.0),
(-PI / 2.0, 0.0, PI / 2.0, 0.0, PI),
(0.0, 0.0, 0.0, PI / 2.0, PI / 2.0),
(0.0, -PI / 2.0, 0.0, PI / 2.0, PI),
(1.0, -PI / 2.0, -1.0, PI / 2.0, PI),
(2.0, -PI / 2.0, -2.0, PI / 2.0, PI),
(3.0, -PI / 2.0, -3.0, PI / 2.0, PI),
(3.0, -PI / 2.0 + 0.5, -3.0, PI / 2.0 + 0.5, PI),
(0.0, 0.0, 0.0, PI, PI),
(PI / 2.0, 1.0, PI / 2.0, 2.0, 0.0),
(-PI / 2.0, 1.0, -PI / 2.0, 2.0, 0.0),
(0.0, 0.0, -PI / 4.0, 0.0, PI / 4.0),
(0.0, 1.0, PI / 4.0, 1.0, PI / 4.0),
(-PI / 2.0, 0.0, -PI / 4.0, 0.0, PI / 4.0),
(-PI / 2.0, 0.0, -PI / 4.0, 0.6, PI / 4.0),
(-PI / 2.0, 3.0, -PI / 4.0, 0.2, PI / 4.0),
].mapIt:
(id: fmt"posA=({it[0]}, {it[1]}), posB=({it[2]}, {it[3]})",
latitudeA: it[0], longitudeA: it[1],
latitudeB: it[2], longitudeB: it[3],
expected: it[4])

func isClose(a, b: float): bool =
return abs(a-b) < 0.0000001

for tc in testCases:
test tc.id:
checkpoint("returns expected result")
check isClose(haversineDistance(tc.latitudeA, tc.longitudeA,
tc.latitudeB, tc.longitudeB), tc.expected)
check isClose(haversineDistance(tc.latitudeB, tc.longitudeB,
tc.latitudeA, tc.longitudeA), tc.expected)