Macro mapcomp::btreemapc

macro_rules! btreemapc {
    (@__ $acc:ident, $key:expr => $val:expr; for $item:pat in $iter:expr; if $cond:expr) => { ... };
    (@__ $acc:ident, $key:expr => $val:expr; for $item:pat in $iter:expr) => { ... };
    (@__ $acc:ident, $key:expr => $val:expr; for $item:pat in $iter:expr; if $cond:expr; $($tail:tt)+) => { ... };
    (@__ $acc:ident, $key:expr => $val:expr; for $item:pat in $iter:expr; $($tail:tt)+) => { ... };
    ($key:expr => $val:expr; $($tail:tt)+) => { ... };
}

BTree Map Comprehension

Creates a BTreeMap from the contents of the comprehension. Same syntax as hashmapc!{}.

let array = [5, 3, 9, 6];

let index_map = hashmapc!{x => i; for (i, x) in array.iter().enumerate()};

for (i, x) in array.iter().enumerate() {
    assert_eq!(index_map[x], i);
}