Example lazy evaluation in Ruby

example.rb

# Note .lazy
txt_files = file_names.lazy.filter { |file_name| file_name.end_with? '.txt' }
file_contents = txt_files = { |file_name| File.read(file_name) }
second_to_last_chars = file_contents.map { |text| text[-2] }
concatenated_characters = second_to_last_chars.reduce { |c, result| result + c }