first() function on a
List is an example of functional programming.
first() is a function that takes a lambda expression as a parameter. A
lambda expression is simply a way of representing an anonymous function.
first() uses the lambda expression, calling it to evaluate the items
in the list. Specifically,
first() iterates through the list until
the lambda expression returns
true for an item in the list (or until
reaches the end of the list).
first() are called higher-order functions: functions that
take functions (e.g., lambda expressions) as parameters.