add geohash

shard.yml

@@ -8,6 +8,8 @@ dependencies:
     github: geocrystal/haversine
   convex_hull:
     github: geocrystal/convex_hull
+  geohash:
+    github: geocrystal/geohash
 
 development_dependencies:
   ameba:

spec/geo/coord_spec.cr

@@ -83,6 +83,15 @@ describe Geo::Coord do
     end
   end
 
+  context "geohash" do
+    context "encode to geohash" do
+      pos = Geo::Coord.new(50.004444, 36.231389)
+
+      it { pos.geohash.should eq("ubcu2rnbuxcx") }
+      it { pos.geohash(5).should eq("ubcu2") }
+    end
+  end
+
   context "to_s" do
     context "is convertible to string" do
       pos = Geo::Coord.new(50.004444, 36.231389)

src/geo.cr

@@ -1,4 +1,5 @@
 require "convex_hull"
+require "geohash"
 require "./geo/utils"
 require "./geo/coord"
 require "./geo/polygon"

src/geo/coord.cr

@@ -146,6 +146,11 @@ module Geo
       end
     end
 
+    # Returns a geohash representing coordinates.
+    def geohash(precision = 12)
+      Geohash.encode(lat.to_f, lng.to_f, precision)
+    end
+
     # Returns a string representing coordinates.
     #
     # ```