佩特图的all_simple_paths()函数需要什么类型的注释？

Question

我正在尝试使用Petgraph的all_simple_paths()，但是我不确定需要什么类型的注释，文档没有给出一个例子。它返回一个impl Iterator<Item = TargetColl>，其中TargetColl: FromIterator<G::NodeId>，但我不知道我应该为它做什么样的注释。

for path in algo::all_simple_paths(&graph, x, y, 0, None) {}

error[E0282]: type annotations needed
   --> lib.rs:10:29
   |
10 | for path in algo::all_simple_paths(&graph, x, y, 0, None) {}
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the element type for this iterator is not specified

Answer 1

它应该足够使用了

for path in algo::all_simple_paths::<Vec<_>, _>(&graph, x, y, 0, None) {}

下面是一个有用的例子：

use petgraph::{algo, prelude::*};

fn main() {
    let mut graph = DiGraph::<&str, i32>::new();

    let a = graph.add_node("a");
    let b = graph.add_node("b");
    let c = graph.add_node("c");
    let d = graph.add_node("d");

    graph.extend_with_edges(&[
        (a, b, 1),
        (b, c, 1),
        (c, d, 1),
        (a, b, 1),
        (b, d, 1),
    ]);

    let ways = algo::all_simple_paths::<Vec<_>, _>(&graph, a, d, 0, None)
        .collect::<Vec<_>>();

    assert_eq!(4, ways.len());
}