将 petgraph Dot 写入文件

Question

我可能遗漏了一些非常基本的东西——我是 Rust 的新手。我正在尝试将 petgraph::dot::Dot 表示写入文件。

以下小代码示例无法编译：

use petgraph::Graph;
use petgraph::dot::{Dot, Config};
use std::fs::File;
use std::io::Write;


fn main() {
    println!("hello graph!");
    let mut graph = Graph::<_, ()>::new();
    graph.add_node("A");
    graph.add_node("B");
    graph.add_node("C");
    graph.add_node("D");
    graph.extend_with_edges(&[
        (0, 1), (0, 2), (0, 3),
        (1, 2), (1, 3),
        (2, 3),
    ]);

    println!("{:?}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
    let mut f = File::create("example1.dot").unwrap();
    let output = format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
    f.write_all(&output.as_bytes());
}

这是编译器错误输出：

error[E0277]: `()` doesn't implement `std::fmt::Display`
  --> examples/graphviz.rs:21:32
   |
21 |     let output = format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `()`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
   = note: required because of the requirements on the impl of `std::fmt::Display` for `petgraph::dot::Dot<'_, &petgraph::graph_impl::Graph<&str, ()>>`
   = note: required by `std::fmt::Display::fmt`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.

petgraph 文档指出 Dot implements Display trait and I based my code on sample code in trait.Display doc

我可以通过将格式字符串更改为 {:?} 让代码正常工作，但我认为这只是为了调试。有没有更好的方法来编写代码来完成同样的事情？

Answer 1

Dot 仅当边和节点权重都实现 Display.

时才实现 Display

由于你的边是()，你不能显示这个图。

例如，更改图形声明以使用 i32 边权重：

    let mut graph = Graph::<_, i32>::new();

使程序编译无误。

将 petgraph Dot 写入文件

writing petgraph Dot to a file

rust

petgraph