Add a JSON addition for Enumerator::ArithmeticSequence

lib/json.rb

@@ -408,6 +408,7 @@
 # - Complex: <tt>require 'json/add/complex'</tt>
 # - Date: <tt>require 'json/add/date'</tt>
 # - DateTime: <tt>require 'json/add/date_time'</tt>
+# - Enumerator::ArithmeticSequence: <tt>require 'json/add/arithmetic_sequence'</tt>
 # - Exception: <tt>require 'json/add/exception'</tt>
 # - OpenStruct: <tt>require 'json/add/ostruct'</tt>
 # - Range: <tt>require 'json/add/range'</tt>

lib/json/add/arithmetic_sequence.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require 'json' unless defined?(JSON::JSON_LOADED) && JSON::JSON_LOADED
+
+class Enumerator
+  class ArithmeticSequence
+    # See #as_json.
+    def self.json_create(object)
+      Range.new(*object.values_at('b', 'e', 'x')) % object['s']
+    end
+
+    # Methods <tt>Enumerator::ArithmeticSequence#as_json</tt> and
+    # +Enumerator::ArithmeticSequence.json_create+ can be used to serialize and
+    # deserialize an \ArithmeticSequence object. See Marshal[rdoc-ref:Marshal].
+    #
+    # \Method <tt>Enumerator::ArithmeticSequence#as_json</tt> serializes +self+,
+    # returning a 5-element hash representing +self+:
+    #
+    #   require 'json/add/arithmetic_sequence'
+    #
+    #   x = 42.step(by: 3, to: 72).as_json
+    #   # => {"json_class"=>"Enumerator::ArithmeticSequence", "b"=>42, "e"=>72, "x"=>false, "s"=>3}
+    #
+    #   y = ((42...72) % 4).as_json
+    #   # => {"json_class"=>"Enumerator::ArithmeticSequence", "b"=>42, "e"=>72, "x"=>true, "s"=>4}
+    #
+    # \Method +JSON.create+ deserializes such a hash, returning an
+    # \ArithmeticSequence object:
+    #
+    #   Enumerator::ArithmeticSequence.json_create(x) # => ((42..72).%(3))
+    #   Enumerator::ArithmeticSequence.json_create(y) # => ((42...72).%(4))
+    #
+    def as_json(*)
+      {
+        JSON.create_id => self.class.name,
+        'b' => self.begin,
+        'e' => self.end,
+        'x' => exclude_end?,
+        's' => step
+      }
+    end
+
+    # Returns a JSON string representing +self+:
+    #
+    #   require 'json/add/arithmetic_sequence'
+    #
+    #   puts 42.step(by: 3, to: 72).to_json
+    #   puts ((42...72) % 4).to_json
+    #
+    # Output:
+    #
+    #   {"json_class":"Enumerator::ArithmeticSequence","b":42,"e":72,"x":false,"s":3}
+    #   {"json_class":"Enumerator::ArithmeticSequence","b":42,"e":72,"x":true,"s":4}
+    #
+    def to_json(*args)
+      as_json.to_json(*args)
+    end
+  end
+end

tests/json_addition_test.rb

@@ -1,5 +1,6 @@
 #frozen_string_literal: false
 require_relative 'test_helper'
+require 'json/add/arithmetic_sequence'
 require 'json/add/core'
 require 'json/add/complex'
 require 'json/add/rational'
@@ -196,4 +197,11 @@ def test_set
     s = Set.new([:a, :b, :c, :a])
     assert_equal s, JSON.parse(JSON(s), :create_additions => true)
   end
+
+  def test_arithmetic_sequence
+    include_end = 42.step(by: 3, to: 72)
+    assert_equal include_end, JSON.parse(JSON(include_end), :create_additions => true)
+    exclude_end = ((42...72) % 4)
+    assert_equal exclude_end, JSON.parse(JSON(exclude_end), :create_additions => true)
+  end
 end