extension Sequence {
func clump(by clumpsize:Int) -> [[Element]] {
let slices : [[Element]] = self.reduce(into:[]) {
memo, cur in
if memo.count == 0 {
return memo.append([cur])
}
if memo.last!.count < clumpsize {
memo.append(memo.removeLast() + [cur])
} else {
memo.append([cur])
}
}
return slices
}
}
let arr = [1, 2, 3, 4, 5]
arr.clump(by:2)
// [[1, 2], [3, 4], [5]]
