Now let's take apart the code of some of our previous example programs.

The following appeared in the simple examples chapter.

def fact(n)
  if n == 0
    1
  else
    n * fact(n-1)
  end
end
print fact(ARGV[0].to_i), "\n"

Because this is …

Let's put together a more interesting program. This time we test whether a string fits a description, encoded into a concise pattern .

There are some characters and character combinations that have special meaning in these patterns, including:

[] - …