Merge pull request #12 from geocrystal/destination

Calculates the location of a destination coord

README.md

@@ -171,6 +171,19 @@ new_york.distance(london).to_kilometers
 # => 5570.4744596620685
 ```
 
+### Calculates the location of a destination coord
+
+```crystal
+require "geo"
+require "geo/distance"
+
+point = Geo::Coord.new(39, -75)
+
+point.destination(5000, 90, :kilometers)
+# Geo::Coord(@lat=26.440010707631124, @lng=-22.885355549364313)
+```
+
+
 ## Contributing
 
 1. Fork it (<https://github.com/geocrystal/geo/fork>)

shard.yml

@@ -6,7 +6,7 @@ crystal: ">= 1.0.0"
 dependencies:
   haversine:
     github: geocrystal/haversine
-    version: ">= 0.4.0"
+    version: ">= 0.5.0"
   convex_hull:
     github: geocrystal/convex_hull
     version: ">= 0.6.0"

spec/geo/distance_spec.cr

@@ -4,11 +4,18 @@ require "../../src/geo/distance"
 describe Geo::Coord do
   london = Geo::Coord.new(51.500153, -0.126236)
   new_york = Geo::Coord.new(40.714268, -74.005974)
+  point = Geo::Coord.new(39, -75)
 
   context "distance" do
     context "calculates distance (by haversine formula)" do
       it { london.distance(london).to_kilometers.should eq(0) }
       it { new_york.distance(london).to_kilometers.should eq(5570.482153929098) }
     end
   end
+
+  context "destination" do
+    context "Calculates the location of a destination point (by haversine formula)" do
+      it { point.destination(5000, 90, :kilometers).should eq(Geo::Coord.new(26.440010707631124, -22.885355549364313)) }
+    end
+  end
 end

src/geo/distance.cr

@@ -7,5 +7,12 @@ module Geo
     def distance(other : Geo::Coord) : Haversine::Distance
       Haversine.distance(self.ll, other.ll)
     end
+
+    # Calculates the location of a destination point
+    def destination(distance : Number, bearing : Number, unit : Symbol = :kilometers) : Geo::Coord
+      point = Haversine.destination(self.ll, distance, bearing, unit)
+
+      Geo::Coord.new(point[0], point[1])
+    end
   end
 end