Update listing code in ch03

Signed-off-by: Sefank <[email protected]>

listings/ch03-common-programming-concepts/listing-03-02/src/main.rs

@@ -2,5 +2,5 @@ fn main() {
     let condition = true;
     let number = if condition { 5 } else { 6 };
 
-    println!("The value of number is: {}", number);
+    println!("The value of number is: {number}");
 }

listings/ch03-common-programming-concepts/listing-03-03/src/main.rs

@@ -2,7 +2,7 @@ fn main() {
     let mut number = 3;
 
     while number != 0 {
-        println!("{}!", number);
+        println!("{number}!");
 
         number -= 1;
     }

listings/ch03-common-programming-concepts/listing-03-05/src/main.rs

@@ -2,6 +2,6 @@ fn main() {
     let a = [10, 20, 30, 40, 50];
 
     for element in a {
-        println!("the value is: {}", element);
+        println!("the value is: {element}");
     }
 }

listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/output.txt

@@ -8,7 +8,7 @@ error[E0384]: cannot assign twice to immutable variable `x`
   |         |
   |         first assignment to `x`
   |         help: consider making this binding mutable: `mut x`
-3 |     println!("The value of x is: {}", x);
+3 |     println!("The value of x is: {x}");
 4 |     x = 6;
   |     ^^^^^ cannot assign twice to immutable variable
 

listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/src/main.rs

@@ -1,6 +1,6 @@
 fn main() {
     let x = 5;
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
     x = 6;
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }

listings/ch03-common-programming-concepts/no-listing-02-adding-mut/src/main.rs

@@ -1,6 +1,6 @@
 fn main() {
     let mut x = 5;
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
     x = 6;
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }

listings/ch03-common-programming-concepts/no-listing-03-shadowing/src/main.rs

@@ -5,8 +5,8 @@ fn main() {
 
     {
         let x = x * 2;
-        println!("The value of x in the inner scope is: {}", x);
+        println!("The value of x in the inner scope is: {x}");
     }
 
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }

listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/src/main.rs

@@ -1,17 +1,17 @@
 fn main() {
-    // 加法
+    // addition
     let sum = 5 + 10;
 
-    // 减法
+    // subtraction
     let difference = 95.5 - 4.3;
 
-    // 乘法
+    // multiplication
     let product = 4 * 30;
 
-    // 除法
+    // division
     let quotient = 56.7 / 32.2;
-    let floored = 2 / 3; // 结果为 0
+    let floored = 2 / 3; // Results in 0
 
-    // 取余
+    // remainder
     let remainder = 43 % 5;
 }

listings/ch03-common-programming-concepts/no-listing-08-boolean/src/main.rs

@@ -1,5 +1,5 @@
 fn main() {
     let t = true;
 
-    let f: bool = false; // 显式指定类型注解
+    let f: bool = false; // with explicit type annotation
 }

listings/ch03-common-programming-concepts/no-listing-09-char/src/main.rs

@@ -1,5 +1,5 @@
 fn main() {
     let c = 'z';
-    let z = 'ℤ';
+    let z: char = 'ℤ'; // with explicit type annotation
     let heart_eyed_cat = '😻';
 }

listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/src/main.rs

@@ -3,5 +3,5 @@ fn main() {
 
     let (x, y, z) = tup;
 
-    println!("The value of y is: {}", y);
+    println!("The value of y is: {y}");
 }

listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/src/main.rs

@@ -18,8 +18,5 @@ fn main() {
 
     let element = a[index];
 
-    println!(
-        "The value of the element at index {} is: {}",
-        index, element
-    );
+    println!("The value of the element at index {index} is: {element}");
 }

listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/src/main.rs

@@ -3,5 +3,5 @@ fn main() {
 }
 
 fn another_function(x: i32) {
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }

listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/src/main.rs

@@ -3,5 +3,5 @@ fn main() {
 }
 
 fn print_labeled_measurement(value: i32, unit_label: char) {
-    println!("The measurement is: {}{}", value, unit_label);
+    println!("The measurement is: {value}{unit_label}");
 }

listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/output.txt

@@ -8,14 +8,13 @@ error: expected expression, found statement (`let`)
   |
   = note: variable declaration using `let` is a statement
 
-error[E0658]: `let` expressions in this position are experimental
+error[E0658]: `let` expressions in this position are unstable
  --> src/main.rs:2:14
   |
 2 |     let x = (let y = 6);
   |              ^^^^^^^^^
   |
   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-  = help: you can write `matches!(<expr>, <pattern>)` instead of `let <pattern> = <expr>`
 
 warning: unnecessary parentheses around assigned value
  --> src/main.rs:2:13

listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/src/main.rs

@@ -4,5 +4,5 @@ fn main() {
         x + 1
     };
 
-    println!("The value of y is: {}", y);
+    println!("The value of y is: {y}");
 }

listings/ch03-common-programming-concepts/no-listing-21-function-return-values/src/main.rs

@@ -5,5 +5,5 @@ fn five() -> i32 {
 fn main() {
     let x = five();
 
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }

listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/src/main.rs

@@ -1,7 +1,7 @@
 fn main() {
     let x = plus_one(5);
 
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }
 
 fn plus_one(x: i32) -> i32 {

listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/src/main.rs

@@ -1,7 +1,7 @@
 fn main() {
     let x = plus_one(5);
 
-    println!("The value of x is: {}", x);
+    println!("The value of x is: {x}");
 }
 
 fn plus_one(x: i32) -> i32 {

listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/src/main.rs

@@ -3,5 +3,5 @@ fn main() {
 
     let number = if condition { 5 } else { "six" };
 
-    println!("The value of number is: {}", number);
+    println!("The value of number is: {number}");
 }

listings/ch03-common-programming-concepts/no-listing-32-5-loop-labels/src/main.rs

@@ -1,11 +1,11 @@
 fn main() {
     let mut count = 0;
     'counting_up: loop {
-        println!("count = {}", count);
+        println!("count = {count}");
         let mut remaining = 10;
 
         loop {
-            println!("remaining = {}", remaining);
+            println!("remaining = {remaining}");
             if remaining == 9 {
                 break;
             }
@@ -17,5 +17,5 @@ fn main() {
 
         count += 1;
     }
-    println!("End count = {}", count);
+    println!("End count = {count}");
 }

listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/src/main.rs

@@ -9,5 +9,5 @@ fn main() {
         }
     };
 
-    println!("The result is {}", result);
+    println!("The result is {result}");
 }

listings/ch03-common-programming-concepts/no-listing-34-for-range/src/main.rs

@@ -1,6 +1,6 @@
 fn main() {
     for number in (1..4).rev() {
-        println!("{}!", number);
+        println!("{number}!");
     }
     println!("LIFTOFF!!!");
 }