add Enumerable#first to mruby-enum-ext

1 files changed, 26 insertions, 0 deletions

diff --git a/mrbgems/mruby-enum-ext/mrblib/enum.rb b/mrbgems/mruby-enum-ext/mrblib/enum.rb
index f250d39f1..85779ee59 100644
--- a/mrbgems/mruby-enum-ext/mrblib/enum.rb
+++ b/mrbgems/mruby-enum-ext/mrblib/enum.rb
@@ -161,4 +161,30 @@ module Enumerable
     h
   end
 
+  NONE = Object.new
+  ##
+  # call-seq:
+  #    enum.first       ->  obj or nil
+  #    enum.first(n)    ->  an_array
+  #
+  # Returns the first element, or the first +n+ elements, of the enumerable.
+  # If the enumerable is empty, the first form returns <code>nil</code>, and the
+  # second form returns an empty array.
+  def first(n=NONE)
+    if n == NONE
+      self.each do |e|
+        return e
+      end
+      return nil
+    else
+      a = []
+      i = 0
+      self.each do |e|
+        break if n<=i
+        a.push e
+        i += 1
+      end
+      a
+    end
+  end
 end