2。循环之后，我们通过分 号结束赋值给 result 的语句。最后打印出 result 的值，也就是 20。 循环标签：在多个循环之间消除歧义 如果存在嵌套循环，break 和 continue 应用于此时最内层的循环。你可以选择在一个循环上 指定一个 循环标签（loop label），然后将标签与 break 或 continue 一起使用，使这些关键字 应用于已标记的循环而不是最内层的循环。下面是一个包含两个嵌套循环的示例： count += 1; } println!("End count = {count}"); } 外层循环有一个标签 counting_up，它将从 0 数到 2。没有标签的内部循环从 10 向下数到 9。 第一个没有指定标签的 break 将只退出内层循环。break 'counting_up; 语句将退出外层循环。 这个代码打印： $ cargo run Compiling 文件名：src/main.rs use std::collections::HashMap; fn main() { let mut map = HashMap::new(); map.insert(1, 2); } 示例 7-14: 将 HashMap 引入作用域的习惯用法 这种习惯用法背后没有什么硬性要求：它只是一种惯例，人们已经习惯了以这种方式阅读和编 写 Rust 代码。 这个习惯用法有一个例外，那就是我们想使用

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x end The power of the try/catch idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet concatenates them. """ function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x end The power of the try/catch idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet concatenates them. """ function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 236 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 236 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 236 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet concatenates them. """ function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 237 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 237 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *

to return the value of x in case of an error: try bad() catch x end Instead, use a semicolon or insert a line break after catch: try bad() catch; x end try bad() catch x endCHAPTER 10. CONTROL FLOW idea for complex functions with many arguments (in particular keyword arguments). In that case, insert it after the general description of the function, under an # Arguments header, with one - bullet DOCUMENTATION 237 function *(x::AbstractString, y::AbstractString, z::AbstractString...) # ... [insert secret sauce here] ... end help?> * search: * .* *(x, y, z...) Multiplication operator. x *