func merge(data, aux sortable.Interface, start, mid, end int) {
i, j := start, mid+1
for k := start; k <= end; k++ {
aux.Set(k, data.Get(k))
}
for k := start; k <= end; k++ {
if i > mid {
data.Set(k, aux.Get(j))
j = j + 1
} else if j > end {
data.Set(k, aux.Get(i))
i = i + 1
} else if aux.Less(i, j) {
data.Set(k, aux.Get(i))
i = i + 1
} else {
data.Set(k, aux.Get(j))
j = j + 1
}
}
}
