Macro comprehension::product

macro_rules! product {
    ($($rest:tt)*) => { ... };
}

Product of iterator comprehension

product![...] is same as iter![...].product() excepting output type will be inferred.

use comprehension::product;

let s = product![i; i <- 1..=10]; // this compiles
// let s = iter![i; i <- 1..=10].product(); // this does not compile