This is an example why functional programming is so expressive: data structures are equivalent to the constructor expressions that created them. Combine this with pattern matching on these constructor expressions and your program becomes a mathematical function definition instead of tons of boilerplate "getter/setter", "do this then do that" boredom.
Consider this little exercise:
Given a list start from the beginning of the list and swap list element pairs. Tail elements not forming a pair stay unchanged.
Examples:
[1,2,3,4,5,6,7] -> [2,1,4,3,6,5,7]
[1] -> [1]
[] -> []
In Scala you write:
def swapPairs[a](xs:List[a]):List[a] = xs match {
case Nil => xs
case List(x) => xs
case x :: y :: ys => y :: x :: swapPairs(ys)
}
This is exactly how you would think about the problem: if the list starts with at least two elements swap those and consider the rest list. Trivial example, true.
You could probably write a pretty simple program in an imperative language like Java to solve the same thing but I suspect it would still contain a lot more handholding code, you would have to spell it out more to the machine and tell it step by step what you want: take the value from here and put it there...etc.
Scala By Example has a better showcase of this language feature: working with abstract syntax trees generated by a parser.
