class Array
  def select! # :yield: x
    i = 0
    each_with_index { |x, j|
      yield x or next
      self[i] = x if i != j
      i += 1
    }
    return nil if i == size
    self[i..-1] = []
    self
  end unless method_defined?(:select!)

  def sort_by!(&block) # :yield: x
    replace(sort_by(&block))
  end unless method_defined?(:sort_by!)
end

class Hash
  class << self
    def try_convert(object)
      if object.is_a?(Hash) ||
          (object.respond_to?(:to_hash) && (object = object.to_hash).is_a?(Hash))
        object
      else
        nil
      end
    end unless method_defined?(:try_convert)
  end
end

class String
  class << self
    def try_convert(object)
      if object.is_a?(String) ||
          (object.respond_to?(:to_str) && (object = object.to_str).is_a?(String))
        object
      else
        nil
      end
    end unless method_defined?(:try_convert)
  end
end

# In Ruby < 1.9.3 URI() does not accept a URI object.
if RUBY_VERSION < "1.9.3"
  require 'uri'

  begin
    URI(URI(''))
  rescue
    def URI(url) # :nodoc:
      case url
      when URI
        url
      when String
        URI.parse(url)
      else
        raise ArgumentError, 'bad argument (expected URI object or URI string)'
      end
    end
  end
end