Macro comprehension::sum

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

Sum of iterator comprehension

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

use comprehension::sum;

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