In this section, we will be expanding on our knowledge of regular expressions by discussing the atom. We will be covering the concept of an atom. An atom is a single expression such as a character or a dot, or an expression that has been defined using parentheses or - as we will see in a further section- the character class. We will also introduce atom modifiers. The idea is that you can take any atom, and then modify it using a modifier. Now, let's go back to our RegexLearning notebook and continue from where we left off in the last section.
Imagine that you have a string representing a date in the year-month-day separated by a dashes format, and you wish to verify that this date is in the 1900s or the 2000s. So, let's say that we have a date of 1969-07-20, and we wish to verify that this date is in either the 1900s or the 2000s:
Well, we crafted...
