Inspired by "FP Concepts" talk by @martinosis at Ruby Montreal.

foo_test.rb

require "minitest/autorun"

module Foo
  attr :add, :sub, :mul, :div

  def initialize(*)
    @add = -> (a, b) { a + b }.curry
    @sub = -> (a, b) { a - b }.curry
    @mul = -> (a, b) { a * b }.curry
    @div = -> (a, b) { a / b }.curry
    super
  end
end

class FooTest < Minitest::Test
  include Foo

  def test_add
    assert_equal 3, add.(1, 2)
  end

  def test_add_sequence
    assert_equal 5, add.(2).(3)
  end

  def test_add_with_curry
    add2 = add.(2)
    assert_equal 7, add2.(5)
  end

  def test_sub
    assert_equal 5, sub.(7, 2)
  end
end