Macro velcro::map_iter

map_iter!() { /* proc-macro */ }

Creates an iterator over pairs of values, expressed with map-like syntax. Other collections and iterators may also be interspersed, or “spread”, using the .. operator.

Usage

use velcro::map_iter;

let vec = vec![0, 1, 2, 3];

for (key, value) in map_iter![0: "a", 1: "b", ..(2..=5): "c"] {
   println!("{} = {}", key, value);
}

assert_eq!(
    map_iter! {
        0: "a",
        1: "b",
        ..(2..=5): "c"
    }.collect::<Vec<_>>(),
    vec![(0, "a"), (1, "b"), (2, "c"), (3, "c"), (4, "c"), (5, "c")]
);

A typical use-case for map_iter is to collect into a third party map implementation, not supported by velcro, while still being able to use the velcro spread operator.

For example, IndexMap from the indexmap crate:

use velcro::map_iter;
use indexmap::map::IndexMap;

let map: IndexMap<_, _> = map_iter! {
        ..(0..10): 100,
        1: 200,
        ..(3..5): 300
    }
    .collect();
assert_eq!(map.get(&0).unwrap(), &100);
assert_eq!(map.get(&1).unwrap(), &200);
assert_eq!(map.get(&2).unwrap(), &100);
assert_eq!(map.get(&3).unwrap(), &300);