Kasen

下線(Kasen) ... Underscore.

require 'kasen'

[[1, 2], [3, 4]].map &_[1]
#=> [2, 4]
# is equivalent for [[1, 2], [3, 4]].map { |ary| ary[1] }

&_.to_i.zero?
# is equivalent for
{ |s| s.to_i.zero? }

&_.select(&_.to_i.eql?(1))
# is equivalent for
{ |ary| ary.select { |n| n.to_i.eql?(1) } }

calling any method with _ produces Proc object which is equivalent for calling methods in Proc body.

note: you can use k instead of _ in IRB.

['0', '1', '2'].select &_.to_i.zero?
#=> ["0"]
# is equivalent for ['0', '1', '2'].select { |s| s.to_i.zero? }

[['1', '2'], ['3', '4']].map &_.select(&_.to_i.eql?(1))
#=> [["1"], []]
# is equivalent for [['1', '2'], ['3', '4']].map { |ary| ary.select { |n| n.to_i.eql?(1) } }

Have it your way.

$ echo "gem 'kasen'" >> Gemfile; bundle

or

$ gem install kasen

_(Kernel#_) just returns empty object Kasen.new, all of which methods has been undefined expect for Kasen#to_proc, Kasen#method_missing.

and say, when _ call #to_i(_.to_i), Kasen#method_missing store context(method_name, args, blokc) recursively.

And finnaly Kasen#to_proc returns all contexts as a block.

After checking out the repo, run bin/setup to install dependencies. Then, run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release to create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

MIT license (© 2015 Kazuki Tanaka)