猜数字程序的第一部分请求和处理用户输入，并检查输入是否符合预期的格式。首先，我们会 允许玩家输入一个猜测。在 src/main.rs 中输入示例 2-1 中的代码。 文件名：src/main.rs use std::io; fn main() { println!("Guess the number!"); println!("Please input your guess."); 输入/输出库引入当前作用域。io 库来自于标准库，也被称为 std： use std::io; 默认情况下，Rust 设定了若干个会自动导入到每个程序作用域中的标准库内容，这组内容被 称为 预导入（prelude） 内容。你可以在标准库文档中查看预导入的所有内容。 如果你需要的类型不在预导入内容中，就必须使用 use 语句显式地将其引入作用域。std::io 库提供很多有用的功能，包括接收用户输入的功能。 回忆一下，我们在程序的第一行使用 use std::io; 从标准库中引入了输入/输出功能。现在调 用 io 库中的函数 stdin，这允许我们处理用户输入： io::stdin() .read_line(&mut guess) 如果程序的开头没有使用 use std::io; 引入 io 库，我们仍可以通过把函数调用写成 std::io::stdin 来使用该函数。stdin

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 6.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully view of the other). Unless the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 8.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 6.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully view of the other). Unless the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 8.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type

operations on any combination of predefined numeric types, whether primitive or composite, behave as expected. 7.1 Complex Numbers The global constant im is bound to the complex number i, representing the In particular, you can write C-style string code to process ASCII strings, and they will work as expected, both in terms of performance and semantics. If such code encounters non-ASCII text, it will gracefully of the other). Un- less the function docstring explicitly indicates that aliasing produces the expected result, it is the responsibility of the caller to ensure proper behavior on such inputs. 9.2 Argument-type