def iFib = {
it == 0 ? 0
: it == 1 ? 1
: it > 1 ? (2..it).inject([0,1]){i, j -> [i[1], i[0]+i[1]]}[1]
/*it < 0*/: (-1..it).inject([0,1]){i, j -> [i[1]-i[0], i[0]]}[0]
}