add Enumerable#each_cons

1 files changed, 31 insertions, 0 deletions

diff --git a/mrbgems/mruby-enum-ext/mrblib/enum.rb b/mrbgems/mruby-enum-ext/mrblib/enum.rb
index a9545da98..7116325f7 100644
--- a/mrbgems/mruby-enum-ext/mrblib/enum.rb
+++ b/mrbgems/mruby-enum-ext/mrblib/enum.rb
@@ -82,4 +82,35 @@ module Enumerable
     ary
   end
   
+  ##
+  # call-seq:
+  #   enum.each_cons(n) {...}   ->  nil
+  #
+  # Iterates the given block for each array of consecutive <n>
+  # elements.
+  #
+  # e.g.:
+  #     (1..10).each_cons(3) {|a| p a}
+  #     # outputs below
+  #     [1, 2, 3]
+  #     [2, 3, 4]
+  #     [3, 4, 5]
+  #     [4, 5, 6]
+  #     [5, 6, 7]
+  #     [6, 7, 8]
+  #     [7, 8, 9]
+  #     [8, 9, 10]
+
+  def each_cons(n, &block)
+    raise TypeError, "expected Integer for 1st argument" unless n.kind_of? Integer
+    raise ArgumentError, "invalid size" if n <= 0
+
+    ary = []
+    self.each do |e|
+      ary.shift if ary.size == n
+      ary << e
+      block.call(ary.dup) if ary.size == n
+    end
+  end
+
 end