diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..42f3dce
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,3 @@
+*.rb diff=ruby
+*.gemspec diff=ruby
+
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e5d9c71
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,13 @@
+# See https://help.github.com/articles/ignoring-files for more about ignoring files.
+#
+# If you find yourself ignoring temporary files generated by your text editor
+# or operating system, you probably want to add a global ignore instead:
+#   git config --global core.excludesfile '~/.gitignore_global'
+
+# Ignore bundler config.
+.bundle/
+
+pkg/
+.byebug_history
+
+*.gem
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..8fc4e1e
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,122 @@
+AllCops:
+  TargetRubyVersion: 2.4
+
+# frozen_string_literal: true
+Style/FrozenStringLiteralComment:
+  Enabled: true
+  EnforcedStyle: when_needed
+
+# Prefer &&/|| over and/or.
+Style/AndOr:
+  Enabled: true
+
+# Do not use braces for hash literals when they are the last argument of a
+# method call.
+Style/BracesAroundHashParameters:
+  Enabled: true
+
+# Align `when` with `case`.
+Layout/CaseIndentation:
+  Enabled: true
+
+# Align comments with method definitions.
+Layout/CommentIndentation:
+  Enabled: true
+
+# No extra empty lines.
+Layout/EmptyLines:
+  Enabled: true
+
+# In a regular class definition, no empty lines around the body.
+Layout/EmptyLinesAroundClassBody:
+  Enabled: true
+
+# In a regular method definition, no empty lines around the body.
+Layout/EmptyLinesAroundMethodBody:
+  Enabled: true
+
+# In a regular module definition, no empty lines around the body.
+Layout/EmptyLinesAroundModuleBody:
+  Enabled: true
+
+# Use Ruby >= 1.9 syntax for hashes. Prefer {a: :b} over { :a => :b }.
+Style/HashSyntax:
+  Enabled: true
+
+# Method definitions after `private` or `protected` isolated calls need one
+# extra level of indentation.
+Layout/IndentationConsistency:
+  Enabled: true
+  EnforcedStyle: normal
+
+# Two spaces, no tabs (for indentation).
+Layout/IndentationWidth:
+  Enabled: true
+
+Layout/SpaceAfterColon:
+  Enabled: true
+
+Layout/SpaceAfterComma:
+  Enabled: true
+
+Layout/SpaceAroundEqualsInParameterDefault:
+  Enabled: true
+
+Layout/SpaceAroundKeyword:
+  Enabled: true
+
+Layout/SpaceAroundOperators:
+  Enabled: true
+
+Layout/SpaceBeforeFirstArg:
+  Enabled: true
+
+# Defining a method with parameters needs parentheses.
+Style/MethodDefParentheses:
+  Enabled: true
+
+# Use `foo {}` not `foo{}`.
+Layout/SpaceBeforeBlockBraces:
+  Enabled: true
+
+# Use `foo { bar }` not `foo {bar}`.
+Layout/SpaceInsideBlockBraces:
+  Enabled: true
+
+# Use `{a: 1}` not `{ a:1 }`.
+Layout/SpaceInsideHashLiteralBraces:
+  Enabled: false
+
+Layout/SpaceInsideParens:
+  Enabled: true
+
+# Check quotes usage according to lint rule below.
+Style/StringLiterals:
+  Enabled: true
+  EnforcedStyle: double_quotes
+
+# Detect hard tabs, no hard tabs.
+Layout/Tab:
+  Enabled: true
+
+# Blank lines should not have any spaces.
+Layout/TrailingBlankLines:
+  Enabled: true
+
+# No trailing whitespace.
+Layout/TrailingWhitespace:
+  Enabled: true
+
+# Use quotes for string literals when they are enough.
+Style/UnneededPercentQ:
+  Enabled: true
+
+# Align `end` with the matching keyword or starting expression except for
+# assignments, where it should be aligned with the LHS.
+Lint/EndAlignment:
+  Enabled: true
+  EnforcedStyleAlignWith: variable
+
+# Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
+Lint/RequireParentheses:
+  Enabled: true
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..55bc983
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+ruby-2.4.1
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..98a4f88
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+# Declare your gem"s dependencies in form_core.gemspec.
+# Bundler will treat runtime dependencies like base dependencies, and
+# development dependencies will be added by default to the :development group.
+gemspec
+
+# Declare any dependencies that are still in development here instead of in
+# your gemspec. These might include edge Rails or gems from your path or
+# Git. Remember to move these dependencies to your gemspec before releasing
+# your gem to rubygems.org.
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..876a5ea
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,44 @@
+PATH
+  remote: .
+  specs:
+    yafl (0.0.1)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.3.0)
+    coderay (1.1.2)
+    method_source (0.9.0)
+    minitest (5.10.3)
+    parallel (1.12.0)
+    parser (2.4.0.0)
+      ast (~> 2.2)
+    powerpack (0.1.1)
+    pry (0.11.1)
+      coderay (~> 1.1.0)
+      method_source (~> 0.9.0)
+    rainbow (2.2.2)
+      rake
+    rake (12.1.0)
+    rubocop (0.50.0)
+      parallel (~> 1.10)
+      parser (>= 2.3.3.1, < 3.0)
+      powerpack (~> 0.1)
+      rainbow (>= 2.2.2, < 3.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (~> 1.0, >= 1.0.1)
+    ruby-progressbar (1.9.0)
+    unicode-display_width (1.3.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  minitest
+  pry
+  rake
+  rubocop
+  yafl!
+
+BUNDLED WITH
+   1.15.4
diff --git a/MIT-LICENSE b/MIT-LICENSE
new file mode 100644
index 0000000..7805781
--- /dev/null
+++ b/MIT-LICENSE
@@ -0,0 +1,20 @@
+Copyright 2017 Jun Jiang
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..69ce627
--- /dev/null
+++ b/README.md
@@ -0,0 +1,46 @@
+YAFL
+====
+
+Yet Another Formula Language.
+
+## Usage
+
+TODO
+
+## Installation
+
+Add this line to your Gemfile:
+
+```ruby
+gem "yafl"
+```
+
+Or you may want to include the gem directly from GitHub:
+
+```ruby
+gem "yafl", github: "jasl-lab/yafl"
+```
+
+And then execute:
+
+```sh
+$ bundle
+```
+
+## Contributing
+
+Bug report or pull request are welcome.
+
+### Make a pull request
+
+1. Fork it
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create new Pull Request
+
+Please write unit test with your code if necessary.
+
+## License
+
+The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 0000000..786f61e
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+begin
+  require "bundler/setup"
+rescue LoadError
+  puts "You must `gem install bundler` and `bundle install` to run rake tasks"
+end
+
+require "rdoc/task"
+
+RDoc::Task.new(:rdoc) do |rdoc|
+  rdoc.rdoc_dir = "rdoc"
+  rdoc.title    = "YAFL"
+  rdoc.options << "--line-numbers"
+  rdoc.rdoc_files.include("README.md")
+  rdoc.rdoc_files.include("lib/**/*.rb")
+end
+
+require "bundler/gem_tasks"
+
+require "rake/testtask"
+
+Rake::TestTask.new(:test) do |t|
+  t.libs << "test"
+  t.pattern = "test/*_test.rb"
+  t.verbose = false
+end
+
+task :console do
+  begin
+    require "pry"
+    console = Pry
+  rescue LoadError
+    require "irb"
+    require "irb/completion"
+    console = IRB
+  end
+
+  require "yafl"
+  ARGV.clear
+  console.start
+end
+
+task default: :test
diff --git a/lib/yafl.rb b/lib/yafl.rb
new file mode 100644
index 0000000..630f034
--- /dev/null
+++ b/lib/yafl.rb
@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+module YAFL # :nodoc:
+end
diff --git a/lib/yafl/version.rb b/lib/yafl/version.rb
new file mode 100644
index 0000000..e653741
--- /dev/null
+++ b/lib/yafl/version.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+module YAFL
+  VERSION = "0.0.1"
+end
diff --git a/test/yafl_test.rb b/test/yafl_test.rb
new file mode 100644
index 0000000..ac9e080
--- /dev/null
+++ b/test/yafl_test.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "yafl"
+
+class YAFLTest < Minitest::Test
+  def test_true
+    assert_equal true, true
+  end
+end
diff --git a/yafl.gemspec b/yafl.gemspec
new file mode 100644
index 0000000..c2e4a9e
--- /dev/null
+++ b/yafl.gemspec
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+$LOAD_PATH.push File.expand_path("../lib", __FILE__)
+
+# Maintain your gem's version:
+require "yafl/version"
+
+# Describe your gem and declare its dependencies:
+Gem::Specification.new do |s|
+  s.name        = "yafl"
+  s.version     = YAFL::VERSION
+  s.authors     = ["jasl"]
+  s.email       = ["jasl9187@hotmail.com"]
+  s.homepage    = "https://github.com/jasl-lab/yafl"
+  s.summary     = "YAFL - Yet Another Formula Language."
+  s.description = <<-TEXT.lstrip
+    YAFL - Yet Another Formula Language
+  TEXT
+  s.license = "MIT"
+
+  s.add_development_dependency "pry"
+  s.add_development_dependency "rake"
+  s.add_development_dependency "minitest"
+  s.add_development_dependency "rubocop"
+
+  s.files        = Dir["lib/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
+  s.test_files   = Dir["test/*_test.rb"]
+  s.require_path = "lib"
+end