Added cosine distance function

src/apatite.cr

@@ -132,7 +132,7 @@ module Apatite
     end
   end
 
-  # Compute the cosine similarity between two vectors.
+  # Compute the cosine similarity of two vectors.
   def similarity(x, y)
     dot(x, y) / (
       Math.sqrt(dot(x, x)) *
@@ -140,6 +140,11 @@ module Apatite
     )
   end
 
+  # Compute the cosine distance between two vectors.
+  def cosine(x, y)
+    1.0 - similarity(x, y)
+  end
+
   # Returns the angle between this vector and another in radians.
   # If the vectors are mirrored across their axes this will return `nil`.
   def angle_from(a, b)

src/apatite/linear_algebra/vector.cr

@@ -450,11 +450,16 @@ module Apatite::LinearAlgebra
       Apatite.angle_from(self, vector)
     end
 
-    # Compute the cosine similarity between this vector and another.
+    # Compute the cosine similarity of this vector and another.
     def similarity(other)
       Apatite.similarity(self, other)
     end
 
+    # Compute the cosine distance between this vector and another.
+    def cosine(other)
+      Apatite.cosine(self, other)
+    end
+
     # Returns whether the vectors are parallel to each other.
     def parallel_to?(vector)
       Apatite.parallel_to?(self, vector)