itemops provides some operations on items of Rust language slices.
For summing elements of a slice with a specified step:
```rust let v = vec![3, 7, 4, 2, 8, 5];
asserteq!(v.sumstep(2), 15); asserteq!(v.sumstep(3), 5); ```
For multiplying elements of a slice with a specified step:
```rust let a = [2, 5, 1, 6, 3, 7];
asserteq!(a.productstep(2), 6); asserteq!(a.productstep(3), 12); ```