Add Angle#positive?, Angle#negative? and Angle#zero?

Author: rhannequin

lib/astronoby/angle.rb

@@ -100,6 +100,18 @@ def tan
       Math.tan(radians)
     end
 
+    def positive?
+      radians > 0
+    end
+
+    def negative?
+      radians < 0
+    end
+
+    def zero?
+      radians.zero?
+    end
+
     def str(format)
       case format
       when :dms then to_dms(degrees).format

lib/astronoby/util/trigonometry.rb

@@ -12,9 +12,9 @@ class << self
         #  Edition: MIT Press
         #  Chapter: 4 - Orbits and Coordinate Systems
         def adjustement_for_arctangent(y, x, angle)
-          return angle if y.degrees.positive? && x.degrees.positive?
+          return angle if y.positive? && x.positive?
 
-          if y.degrees.negative? && x.degrees.positive?
+          if y.negative? && x.positive?
             return Angle.as_degrees(angle.degrees + 360)
           end
 

spec/astronoby/angle_spec.rb

@@ -193,6 +193,48 @@
     end
   end
 
+  describe "#positive?" do
+    it "returns true when the angle is positive" do
+      expect(described_class.as_degrees(90).positive?).to be true
+    end
+
+    it "returns false when the angle is negative" do
+      expect(described_class.as_degrees(-90).positive?).to be false
+    end
+
+    it "returns famse when the angle has a zero value" do
+      expect(described_class.as_degrees(0).positive?).to be false
+    end
+  end
+
+  describe "#negative?" do
+    it "returns false when the angle is positive" do
+      expect(described_class.as_degrees(90).negative?).to be false
+    end
+
+    it "returns true when the angle is negative" do
+      expect(described_class.as_degrees(-90).negative?).to be true
+    end
+
+    it "returns false when the angle has a zero value" do
+      expect(described_class.as_degrees(0).negative?).to be false
+    end
+  end
+
+  describe "#zero?" do
+    it "returns false when the angle is positive" do
+      expect(described_class.as_degrees(90).zero?).to be false
+    end
+
+    it "returns false when the angle is negative" do
+      expect(described_class.as_degrees(-90).zero?).to be false
+    end
+
+    it "returns true when the angle has a zero value" do
+      expect(described_class.as_degrees(0).zero?).to be true
+    end
+  end
+
   describe "#str" do
     it "returns a String" do
       angle = described_class.as_degrees(180)