How can I insert an element every $n$ positions in a list?
For example, inserting a zero as every 4th element to turn
{1, 2, 3, 4, 5, 6, 7}
into
{1, 2, 3, 0, 4, 5, 6, 0, 7}
Surely there must be a simpler way than
list = {1, 2, 3, 4, 5, 6, 7};
every = 4;
Insert[list, 0, List /@ Range[1, Floor[Length@list/(every - 1)]]*(every - 1)]