本文主要是介绍RustDay06------Exercise[81-90]，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
81.宏函数里面的不同的匹配规则需要使用分号隔开
// macros4.rs
//
// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONE#[rustfmt::skip]
macro_rules! my_macro {() => {println!("Check out my macro!");};($val:expr) => {println!("Look at this other macro: {}", $val);};
}fn main() {my_macro!();my_macro!(7777);
}
82.使用内部封装好的宏来替代某些常数
// clippy1.rs
//
// The Clippy tool is a collection of lints to analyze your code so you can
// catch common mistakes and improve your Rust code.
//
// For these exercises the code will fail to compile when there are clippy
// warnings check clippy's suggestions from the output to solve the exercise.
//
// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONEuse std::f32;fn main() {let pi = f32::consts::PI;// 3.14f32;let radius = 5.00f32;let area = pi * f32::powi(radius, 2);println!("The area of a circle with radius {:.2} is {:.5}!",radius, area)
}
83.if let回顾
// clippy2.rs
//
// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
// hint.// I AM DONEfn main() {let mut res = 42;let option = Some(12);if let Some(x)=option {res += x;}println!("{}", res);
}
84.按照提示修改
这题说明 resize是原地操作 没有返回值
交换值必须要借助中间变量
// clippy3.rs
//
// Here's a couple more easy Clippy fixes, so you can see its utility.
//
// Execute `rustlings hint clippy3` or use the `hint` watch subcommand for a hint.// I AM NOT DONE#[allow(unused_variables, unused_assignments)]
fn main() {let my_option: Option<()> = None;// if my_option.is_none() {// my_option.unwrap();// }let my_arr = &[-1, -2, -3,-4, -5, -6,];println!("My array! Here it is: {:?}", my_arr);let my_empty_vec = vec![1, 2, 3, 4, 5];println!("This Vec is empty, see? {:?}", my_empty_vec);let mut value_a = 45;let mut value_b = 66;// Let's swap these two!let mut temp =0;temp=value_a;value_a = value_b;value_b = temp;println!("value a: {}; value b: {}", value_a, value_b);
}
85.使用as强制转换类型
// using_as.rs
//
// Type casting in Rust is done via the usage of the `as` operator. Please note
// that the `as` operator is not only used when type casting. It also helps with
// renaming imports.
//
// The goal is to make sure that the division does not fail to compile and
// returns the proper type.
//
// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
// hint.// I AM NOT DONEfn average(values: &[f64]) -> f64 {let total = values.iter().sum::<f64>();total / values.len() as f64
}fn main() {let values = [3.5, 0.3, 13.0, 11.7];println!("{}", average(&values));
}#[cfg(test)]
mod tests {use super::*;#[test]fn returns_proper_type_and_value() {assert_eq!(average(&[3.5, 0.3, 13.0, 11.7]), 7.125);}
}
86.
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