day12

exercises/clippy/clippy1.rs

@@ -6,12 +6,12 @@
 // 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 DONE
+// cargo clippy
 
 use std::f32;
 
 fn main() {
-    let pi = 3.14f32;
+    let pi = f32::consts::PI;
     let radius = 5.00f32;
 
     let area = pi * f32::powi(radius, 2);

exercises/clippy/clippy2.rs

@@ -1,12 +1,10 @@
 // clippy2.rs
 // Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     let mut res = 42;
     let option = Some(12);
-    for x in option {
+    if let Some(x) = option {
         res += x;
     }
     println!("{}", res);

exercises/clippy/clippy3.rs

@@ -1,28 +1,30 @@
 // clippy3.rs
 // Here's a couple more easy Clippy fixes, so you can see its utility.
 
-// I AM NOT DONE
-
 #[allow(unused_variables, unused_assignments)]
 fn main() {
     let my_option: Option<()> = None;
     if my_option.is_none() {
-        my_option.unwrap();
+        // my_option.unwrap();
+        println!("my_option is none");
     }
 
-    let my_arr = &[
-        -1, -2, -3
-        -4, -5, -6
-    ];
+    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].resize(0, 5);
+    let mut my_empty_vec = vec![1, 2, 3, 4, 5];
+    // my_empty_vec.resize(0, 5);
+    my_empty_vec.clear();
     println!("This Vec is empty, see? {:?}", my_empty_vec);
 
     let mut value_a = 45;
     let mut value_b = 66;
     // Let's swap these two!
-    value_a = value_b;
-    value_b = value_a;
+    // value_a = value_b;
+    // value_b = value_a;
+    // let temp = value_a;
+    // value_a = value_b;
+    // value_b = temp;
+    std::mem::swap(&mut value_a, &mut value_b);
     println!("value a: {}; value b: {}", value_a, value_b);
 }

exercises/conversions/from_into.rs

@@ -2,6 +2,7 @@
 // If From is implemented correctly for a type, the Into trait should work conversely.
 // You can read more about it at https://doc.rust-lang.org/std/convert/trait.From.html
 // Execute `rustlings hint from_into` or use the `hint` watch subcommand for a hint.
+use std::num::ParseIntError;
 
 #[derive(Debug)]
 struct Person {
@@ -27,18 +28,50 @@ impl Default for Person {
 // be handled appropriately.
 //
 // Steps:
-// 1. If the length of the provided string is 0, then return the default of Person
-// 2. Split the given string on the commas present in it
-// 3. Extract the first element from the split operation and use it as the name
+// 1. If the length of the provided string is 0, then return the default of Person 如果为0
+//    返回defalut
+// 2. Split the given string on the commas present in it 逗号分割
+// 3. Extract the first element from the split operation and use it as the name 第一个元素
 // 4. If the name is empty, then return the default of Person
 // 5. Extract the other element from the split operation and parse it into a `usize` as the age
+//    提取年龄
 // If while parsing the age, something goes wrong, then return the default of Person
 // Otherwise, then return an instantiated Person object with the results
 
-// I AM NOT DONE
-
 impl From<&str> for Person {
     fn from(s: &str) -> Person {
+        let default = Person::default();
+        let mut p = Person {
+            name: String::from(""),
+            age: 0,
+        };
+        if s.len() == 0 {
+            return default;
+        }
+
+        let person: Vec<&str> = s.split(",").collect();
+        if person.len() != 2 {
+            return default;
+        }
+
+        let name = person[0];
+
+        if name.len() <= 0 {
+            return default;
+        }
+        p.name = name.to_string();
+
+        let age = person[1];
+        let res: Result<usize, ParseIntError> = age.parse();
+        match res {
+            Ok(a) => p.age = a,
+            Err(err) => {
+                println!("{:?}", err);
+                return default;
+            }
+        };
+
+        p
     }
 }
 

exercises/conversions/using_as.rs

@@ -6,11 +6,9 @@
 // and returns the proper type.
 // Execute `rustlings hint using_as` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn average(values: &[f64]) -> f64 {
     let total = values.iter().sum::<f64>();
-    total / values.len()
+    total / values.len() as f64
 }
 
 fn main() {

exercises/macros/macros3.rs

@@ -2,8 +2,6 @@
 // Make me compile, without taking the macro out of the module!
 // Execute `rustlings hint macros3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[macro_use]
 mod macros {
     macro_rules! my_macro {

exercises/macros/macros4.rs

@@ -1,15 +1,14 @@
 // macros4.rs
 // Execute `rustlings hint macros4` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
+#[macro_export]
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
-    }
+    };
     ($val:expr) => {
         println!("Look at this other macro: {}", $val);
-    }
+    };
 }
 
 fn main() {