ch03 一般的なプログラミングの概念の和訳を最新版に更新

rust-lang/book@19c40bf

Author: shinmili

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

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

@@ -10,9 +10,9 @@ error[E0384]: cannot assign twice to immutable variable `x`
   |         first assignment to `x`
   |         (`x`への最初の代入)
   |         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
 
 For more information about this error, try `rustc --explain E0384`.
-error: could not compile `variables` due to previous error
+error: could not compile `variables` (bin "variables") due to 1 previous error

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);     // xの値は{}です
+    println!("The value of x is: {x}");     // xの値は{x}です
     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-05-mut-cant-change-types/output.txt

@@ -8,6 +8,12 @@ error[E0308]: mismatched types          (型が合いません)
 3 |     spaces = spaces.len();
   |              ^^^^^^^^^^^^ expected `&str`, found `usize`
   |                           (&str型を予期しましたが、usizeが見つかりました)
+  |
+help: try removing the method call
+  |
+3 -     spaces = spaces.len();
+3 +     spaces = spaces;
+  |
 
 For more information about this error, try `rustc --explain E0308`.
-error: could not compile `variables` due to previous error
+error: could not compile `variables` (bin "variables") due to 1 previous error

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

@@ -14,8 +14,8 @@ fn main() {
     // division
     // 割り算
     let quotient = 56.7 / 32.2;
-    let floored = 2 / 3; // Results in 0
-                         // 結果は0
+    let truncated = -5 / 3; // Results in -1
+                            // 結果は-1
 
     // remainder
     // 余り

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

@@ -1,5 +1,6 @@
 fn main() {
     let c = 'z';
-    let z = 'ℤ';
+    let z: char = 'ℤ'; // with explicit type annotation
+                       // 明示的型注釈付きで
     let heart_eyed_cat = '😻';    //ハート目の猫
 }

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

@@ -21,9 +21,6 @@ fn main() {
 
     let element = a[index];
 
-    println!(
-        "The value of the element at index {} is: {}",
-        // {}番目の要素の値は{}です
-        index, element
-    );
+    println!("The value of the element at index {index} is: {element}");
+           // {index}番目の要素の値は{element}です
 }

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);   // xの値は{}です
+    println!("The value of x is: {x}");   // xの値は{x}です
 }

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

@@ -1,23 +1,14 @@
 $ cargo run
    Compiling functions v0.1.0 (file:///projects/functions)
-error: expected expression, found statement (`let`)
-(エラー: 式を予期しましたが、文が見つかりました (`let`))
+error: expected expression, found `let` statement
+(エラー: 式を予期しましたが、`let`文が見つかりました)
  --> src/main.rs:2:14
   |
 2 |     let x = (let y = 6);
-  |              ^^^^^^^^^
+  |              ^^^
   |
-  = note: variable declaration using `let` is a statement
-    (注釈: `let`を使う変数宣言は、文です)
-
-error[E0658]: `let` expressions in this position are experimental
- --> 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>`
+  = note: only supported directly in conditions of `if` and `while` expressions
+    (注釈: `if` および `while` 式の条件部直下でのみ対応しています
 
 warning: unnecessary parentheses around assigned value
  --> src/main.rs:2:13
@@ -30,8 +21,7 @@ help: remove these parentheses
   |
 2 -     let x = (let y = 6);
 2 +     let x = let y = 6;
-  | 
+  |
 
-For more information about this error, try `rustc --explain E0658`.
 warning: `functions` (bin "functions") generated 1 warning
-error: could not compile `functions` due to 2 previous errors; 1 warning emitted
+error: could not compile `functions` (bin "functions") due to 1 previous error; 1 warning emitted

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/output.txt

@@ -9,7 +9,7 @@ error[E0308]: mismatched types
   |    |
   |    implicitly returns `()` as its body has no tail or `return` expression
 8 |     x + 1;
-  |          - help: consider removing this semicolon
+  |          - help: remove this semicolon to return this value
 
 For more information about this error, try `rustc --explain E0308`.
-error: could not compile `functions` due to previous error
+error: could not compile `functions` (bin "functions") due to 1 previous error

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-28-if-condition-must-be-bool/output.txt

@@ -9,4 +9,4 @@ error[E0308]: mismatched types
   |               (bool型を予期したのに、整数変数が見つかりました)
 
 For more information about this error, try `rustc --explain E0308`.
-error: could not compile `branches` due to previous error
+error: could not compile `branches` (bin "branches") due to 1 previous error

listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/output.txt

@@ -11,4 +11,4 @@ error[E0308]: `if` and `else` have incompatible types
   |                                 expected because of this
 
 For more information about this error, try `rustc --explain E0308`.
-error: could not compile `branches` due to previous error
+error: could not compile `branches` (bin "branches") due to 1 previous error

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!!!");
 }

listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/output.txt

@@ -1,12 +1,20 @@
 $ cargo build
    Compiling no_type_annotations v0.1.0 (file:///projects/no_type_annotations)
-error[E0282]: type annotations needed
+error[E0284]: type annotations needed
               (型注釈が必要です)
  --> src/main.rs:2:9
   |
 2 |     let guess = "42".parse().expect("Not a number!");
-  |         ^^^^^ consider giving `guess` a type
-  |               (`guess`に型を与えることを検討してください)
+  |         ^^^^^        ----- type must be known at this point
+  |                            (型はこの時点で既知でなくてはなりません)
+  |
+  = note: cannot satisfy `<_ as FromStr>::Err == _`
+          (`<_ as FromStr>::Err == _`を満たすことができません)
+help: consider giving `guess` an explicit type
+  |   (`guess`に型を与えることを検討してください)
+  |
+2 |     let guess: /* Type */ = "42".parse().expect("Not a number!");
+  |              ++++++++++++
 
-For more information about this error, try `rustc --explain E0282`.
-error: could not compile `no_type_annotations` due to previous error
+For more information about this error, try `rustc --explain E0284`.
+error: could not compile `no_type_annotations` (bin "no_type_annotations") due to 1 previous error

src/ch03-00-common-programming-concepts.md

@@ -27,21 +27,23 @@ them early will give you a strong core to start from.
 これらの基礎は全てのRustプログラムに存在するものであり、それらを早期に学ぶことにより、強力な基礎を築くことになるでしょう。
 
 <!--
-> ### Keywords
+> #### Keywords
 >
-> The Rust language has a set of *keywords* that have been reserved for use by
-> the language only, much as in other languages. Keep in mind that you cannot
-> use these words as names of variables or functions. Most of the keywords have
+> The Rust language has a set of *keywords* that are reserved for use by the
+> language only, much as in other languages. Keep in mind that you cannot use
+> these words as names of variables or functions. Most of the keywords have
 > special meanings, and you’ll be using them to do various tasks in your Rust
 > programs; a few have no current functionality associated with them but have
 > been reserved for functionality that might be added to Rust in the future. You
-> can find a list of the keywords in Appendix A.
+> can find a list of the keywords in [Appendix A][appendix_a].
 -->
 
-> ### キーワード
+> #### キーワード
 >
 > Rust言語にも他の言語同様、キーワードが存在し、これらは言語だけが使用できるようになっています。
 > これらの単語は、変数や関数名には使えないことを弁えておいてください。ほとんどのキーワードは、特別な意味を持っており、
 > 自らのRustプログラムにおいて、様々な作業をこなすために使用することができます;
 > いくつかは、紐付けられた機能がないものの、将来Rustに追加されるかもしれない機能用に予約されています。
 > キーワードの一覧は、付録Aで確認できます。
+
+[appendix_a]: appendix-01-keywords.md