The second part of a function definition is the actual computation of the function. In this
second part, often (but not always) some ad hoc variables are provided to the left of the
equal sign that are involved in the computation to the right. Unlike variables in C,
however--and much like variables in mathematics--the Haskell variables refer to the
exact same "unknown quantity" on both sides of the equal sign (not to a "container"
where a value is held)