使用占位符打印Vec

Question

我正在尝试使用其他数据类型的变量打印Vec：

let a = 4;
let b = vec![1,2,3,4];
let c = 3;

// printing input
println!("a: {0}, b: {1}, c: {2}", a, b, c);

但是我收到了这个错误：

error[E0277]: the trait bound `std::vec::Vec<{integer}>: std::fmt::Display` is not satisfied
  --> src/main.rs:23:43
   |
23 |     println!("a: {0}, b: {1}, c: {2}", a, b, c);
   |                                           ^ trait `std::vec::Vec<{integer}>: std::fmt::Display` not satisfied
   |
   = note: `std::vec::Vec<{integer}>` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
   = note: required by `std::fmt::Display::fmt`

如何在输出字符串中的特定位置打印Vec？