Lemo

Yet another memoize gem. Because it does some things that are important to me.

Attention paid to performance:

• rewrites the memoized method for fast normal-path execution. Rewritten method only makes calls to ruby methods, apart from the necessary single call to the original method.

• Uses instance variables for memoisation storage.

Lemo::Memo treats nil as a value, in other words uses presence or absence of an instance variable to establish whether the value has been memoised or not. Can clear one or several or all memoized values.

Lemo::Ormo behaves like @ivar ||= so clearing is just setting @ivar to nil. Or removing it.

_memoed_methods gives a hash of methods that have been memoised, and their unmemoised method bodies.

Works on singleton instances. Although the syntax is clunky and best avoided.

Is just as threadsafe as ||= (in other words it mostly isn't)

Will raise an exception if you attempt to memoise methods with parameters.

Add this line to your application's Gemfile:

gem 'lemo'

And then execute:

$ bundle

Or install it yourself as:

$ gem install lemo

require 'lemo/ormo'

class YourThing
  include Lemo::Ormo # or Lemo::Memo if you want nil-as-a-value and specialised clearing.

  def normal_method
    rand
  end

  memo def expensive_calculation
    # do complicated stuff that is referentially transparent
  end
end

your_thing = YourThing.new
your_thing.expensive_calculation
your_thing.clear_memos

rspec to run specs

Bug reports and pull requests are welcome on GitHub at https://github.com/djellemah/lemo.

The gem is available as open source under the terms of the MIT License.