Repeat is an iterator, so you can apply it to any type you want, not just strings. You can chain it with other iterators, or collect it into some data structure. But yes, repeat(0) returns an empty iterator.
This example makes a repeat(0) but asks for just the first 12 things in it, they are, of course, all twelve zeroes. Feel free to adjust it to ask for more if you think maybe there aren't any more, or they stop being zero.
https://doc.rust-lang.org/std/iter/fn.repeat.html