Error message in terminal

charany1@esaas_course:~/workspace/hw-ruby-intro (master) $ rspec spec/part1_spec.rb 
/usr/local/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': /home/ubuntu/workspace/hw-ruby-intro/lib/ruby_intro.rb:47: syntax error, unexpected end-of-input, expecting keyword_end (SyntaxError)
        from /usr/local/rvm/rubies/ruby-2.2.2/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from /home/ubuntu/workspace/hw-ruby-intro/spec/part1_spec.rb:1:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/configuration.rb:1327:in `load'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/configuration.rb:1327:in `block in load_spec_files'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/configuration.rb:1325:in `each'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/configuration.rb:1325:in `load_spec_files'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/runner.rb:102:in `setup'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/runner.rb:88:in `run'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/runner.rb:73:in `run'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/lib/rspec/core/runner.rb:41:in `invoke'
        from /usr/local/rvm/gems/ruby-2.2.2/gems/rspec-core-3.3.2/exe/rspec:4:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.2.2/bin/rspec:23:in `load'
        from /usr/local/rvm/gems/ruby-2.2.2/bin/rspec:23:in `<main>'
        from /usr/local/rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `eval'
        from /usr/local/rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `<main>'
charany1@esaas_course:~/workspace/hw-ruby-intro (master) $ 

part_1.rb

# When done, submit this entire file to the autograder.

# Part 1

def sum arr
  # YOUR CODE HERE
  answer = 0
  for i in 0...arr.size do
    answer += arr[i]
  end
  answer
end

def max_2_sum arr
  # YOUR CODE HERE
  sorted_arr = arr.sort
  num_elements = arr.size
  if num_elements == 0
    return 0
  else if num_elements == 1
    return sorted_arr[0]
  else
    return sorted_arr[num_elements-1]+sorted_arr[num_elements-2]
  end
end

def sum_to_n? arr, n
  # YOUR CODE HERE
  if arr.size == 0
    return false
  end
  
  sorted_arr = arr.sort
  left_ptr = 0
  right_ptr = arr.size - 1
  while left_ptr<right_ptr do
    if (sorted_arr[left_ptr]+sorted_arr[right_ptr]) == n 
      return true
    else if (sorted_arr[left_ptr]+sorted_arr[right_ptr]) > n
      right_ptr -= 1
    else
      left_ptr += 1
    end
  end
  return false
end