Calling variadic function with iterator in Rust

Question

A variadic function takes a variable number of arguments of same type. Macro function !product from Itertools package are one of those and I'd like to compute it with a vector of ranges.

Example usage of !product is following where each argument is a Range

use itertools::iproduct;

// Iterate over the coordinates of a 4 x 4 x 4 grid
// from (0, 0, 0), (0, 0, 1), .., (0, 1, 0), (0, 1, 1), .. etc until (3, 3, 3)
for (i, j, k) in iproduct!(0..4, 0..4, 0..4) {
    // ..
}

How can I call iproduct with an iterator or a vector where each element will become each argument into iproduct? For instance

use std::ops::Range;

let ranges : Vec<Range<i64>> = vec![
    Range {start: 5, end: 10}, 
    Range {start: 0, end: 10}, 
    Range {start: -2, end: 3}
];

// How to call here properly??
for (i, j, k) in iproduct!(ranges) {
    // ..
}

Side note: For instance in python, one would call the function using the star sign before the variable: product(*ranges).

docs.rs/itertools/latest/itertools/…

PitaJ
– PitaJ

2022-11-07 16:51:37 +00:00
Commented Nov 7, 2022 at 16:51 — PitaJ
– PitaJ, Commented Nov 7, 2022 at 16:51

PitaJ · Accepted Answer · 2022-11-07 17:10:47Z

3

I think you're looking for Itertools::multi_cartesian_product

use itertools::Itertools;
use std::ops::Range;

fn main() {
    let ranges: Vec<Range<i64>> = vec![
        5..10,
        0..10,
        -2..3,
    ];

    // How to call here properly??
    for v in ranges.into_iter().multi_cartesian_product() {
        let i = v[0];
        let j = v[1];
        let k = v[2];
        // ..
    }
}

answered Nov 7, 2022 at 17:10

PitaJ

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2 Comments

Rikard Olsson Over a year ago

Yes, great! Thank you. Just by curiosity, do you know if there is a similar way as in python to call a function with variable number of arguments?

PitaJ Over a year ago

Rust does not have optional or variadic arguments.

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