lib/fat_period/period.rb in fat_period-1.1.1 vs lib/fat_period/period.rb in fat_period-1.2.0

@@ -27,12 +27,13 @@
   # @param last [Date, String] last date of Period
   # @raise [ArgumentError] if string is not parseable as a Date or
   # @raise [ArgumentError] if first date is later than last date
   # @return [Period]
   def initialize(first, last)
-    @first = Date.ensure_date(first)
-    @last = Date.ensure_date(last)
+    @first = Date.ensure_date(first).freeze
+    @last = Date.ensure_date(last).freeze
+    freeze
 
     return unless @first > @last
 
     raise ArgumentError, "Period's first date is later than its last date"
   end
@@ -176,9 +177,23 @@
   end
 
   # Comparable does not include this.
   def !=(other)
     !(self == other)
+  end
+
+  # Return the hash value for this Period.  Make Period's with identical
+  # values test eql? so that they may be used as hash keys.
+  #
+  # @return [Integer]
+  def hash
+    (first.hash | last.hash)
+  end
+
+  def eql?(other)
+    return nil unless other.is_a?(Period)
+
+    hash == other.hash
   end
 
   # Return whether this Period contains the given date.
   #
   # @param date [Date] date to test