PE 2

PE2C#

IEnumerable<int> fib() {
    var s1 = 0;
    var s2 = 1;
    while (true) {
        var o = s1 + s2;
        s1 = s2;
        s2 = o;
        yield return o;
    }   
}
// this is prettier
Func<int,bool> isEven = i => i % 2 == 0;
Func<int,bool> under4Mill = i => i < 4000000;
var sum = fib().Where(isEven).TakeWhile(under4Mill).Sum();
// this is the one liner
sum = fib().Where(i => i % 2 == 0).TakeWhile(i => i < 4000000).Sum();
Console.WriteLine(sum);

PE2Scala

def fib: Stream[Long] = {
  def tail(h: Long, n: Long): Stream[Long] = h #:: tail(n, h + n)
  tail(0, 1)
}
// pretty one 
def even(i: Int) = i % 2 == 0
def under4mill(i: Int) = i < 4000000
fib filter even takeWhile under4mill sum
// one liner
fib filter (_ % 2 == 0) takeWhile (_ < 4000000) sum