Add to_enum unless block

mrbgems/mruby-enum-ext/mrblib/enum.rb

@@ -25,15 +25,20 @@ module Enumerable
   ##
   # call-seq:
   #    enum.drop_while {|arr| block }   -> array
+  #    enum.drop_while                  -> an_enumerator
   #
   # Drops elements up to, but not including, the first element for
   # which the block returns +nil+ or +false+ and returns an array
   # containing the remaining elements.
   #
+  # If no block is given, an enumerator is returned instead.
+  #
   #    a = [1, 2, 3, 4, 5, 0]
   #    a.drop_while {|i| i < 3 }   #=> [3, 4, 5, 0]
 
   def drop_while(&block)
+    return to_enum :drop_while unless block_given?
+
     ary, state = [], false
     self.each do |*val|
       state = true if !state and !block.call(*val)
@@ -67,15 +72,19 @@ module Enumerable
   ##
   # call-seq:
   #    enum.take_while {|arr| block }   -> array
+  #    enum.take_while                  -> an_enumerator
   #
   # Passes elements to the block until the block returns +nil+ or +false+,
   # then stops iterating and returns an array of all prior elements.
   #
+  #  If no block is given, an enumerator is returned instead.
   #
   #    a = [1, 2, 3, 4, 5, 0]
   #    a.take_while {|i| i < 3 }   #=> [1, 2]
 
   def take_while(&block)
+    return to_enum :take_while unless block_given?
+
     ary = []
     self.each do |*val|
       return ary unless block.call(*val)
@@ -149,6 +158,7 @@ module Enumerable
   ##
   # call-seq:
   #    enum.group_by {| obj | block }  -> a_hash
+  #    enum.group_by                   -> an_enumerator
   #
   # Returns a hash, which keys are evaluated result from the
   # block, and values are arrays of elements in <i>enum</i>
@@ -157,6 +167,8 @@ module Enumerable
   #    (1..6).group_by {|i| i%3}   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}
 
   def group_by(&block)
+    return to_enum :group_by unless block_given?
+
     h = {}
     self.each do |*val|
       key = block.call(*val)
@@ -169,10 +181,16 @@ module Enumerable
   ##
   # call-seq:
   #    enum.sort_by { |obj| block }   -> array
+  #    enum.sort_by                   -> an_enumerator
   #
   # Sorts <i>enum</i> using a set of keys generated by mapping the
   # values in <i>enum</i> through the given block.
+  #
+  # If no block is given, an enumerator is returned instead.
+
   def sort_by(&block)
+    return to_enum :sort_by unless block_given?
+
     ary = []
     orig = [] 
     self.each_with_index{|e, i|
@@ -393,6 +411,8 @@ module Enumerable
   #     %w(albatross dog horse).minmax_by { |x| x.length }   #=> ["dog", "albatross"]
 
   def minmax_by(&block)
+    return to_enum :minmax_by unless block_given?
+
     max = nil
     max_cmp = nil
     min = nil
@@ -522,6 +542,8 @@ module Enumerable
   #
 
   def reverse_each(&block)
+    return to_enum :reverse_each unless block_given?
+
     ary = self.to_a
     i = ary.size - 1
     while i>=0