“宏未定义"；当使用scan读取u8时！() [英] "macro undefined" when reading u8 using scan!()

问题描述

我读到有关读取

I read about reading integer input in How to read an integer input from the user in Rust 1.0?, but I noticed that all the solutions first take a string as input and then convert it to integer. I wonder if there's a way to read an integer directly.

此页面提到了scan!()宏，但是由于某些原因，它没有当我使用rustc main.rc编译以下程序时，似乎没有运行.

This page mentions scan!() macro but for some reason it doesn't seem to run when I compile the following program using rustc main.rc.

extern crate text_io;

fn main() {
    let mut a: u8;
    let mut b: u8;
    scan!("{},{}", a, b);
    print!("{} {}", a, b);
}

这会产生错误:

error: macro undefined: 'scan!'
    scan!("{},{}",a,b);

推荐答案

您必须明确地说您要从此板条箱中导入宏:

You have to explicitly say that you want to import macros from this crate:

#[macro_use] extern crate text_io;

本文写在自述文件的最顶部，您一定错过了.

This is written at the very top of the readme, you must have missed it.

要使用crates.io中的包装箱，您需要将其添加到Cargo.toml中，例如，通过将以下行添加到该文件中:

To use crates from crates.io, you need to add them to your Cargo.toml, for example by adding the following lines to that file:

[dependencies]
text_io = "0.1"

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