ch04 所有権を理解するの和訳を最新版に更新

rust-lang/book@19c40bf

Author: shinmili

listings/ch04-understanding-ownership/listing-04-01/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-01/src/main.rs

@@ -1,9 +1,9 @@
 fn main() {
     // ANCHOR: here
-    {                      // s is not valid here, it’s not yet declared
-        let s = "hello";   // s is valid from this point forward
+    {                      // sは、ここでは有効ではない。まだ宣言されていない
+        let s = "hello";   // sは、ここから有効になる
 
-        // do stuff with s
-    }                      // this scope is now over, and s is no longer valid
+        // sで作業をする
+    }                      // このスコープは終わり。もうsは有効ではない
     // ANCHOR_END: here
 }

listings/ch04-understanding-ownership/listing-04-02/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-03/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-03/src/main.rs

@@ -1,23 +1,23 @@
 fn main() {
-    let s = String::from("hello");  // s comes into scope
+    let s = String::from("hello");  // sがスコープに入る
 
-    takes_ownership(s);             // s's value moves into the function...
-                                    // ... and so is no longer valid here
+    takes_ownership(s);             // sの値が関数にムーブされ...
+                                    // ... ここではもう有効ではない
 
-    let x = 5;                      // x comes into scope
+    let x = 5;                      // xがスコープに入る
 
-    makes_copy(x);                  // x would move into the function,
-                                    // but i32 is Copy, so it’s okay to still
-                                    // use x afterward
+    makes_copy(x);                  // xも関数にムーブされるが、
+                                    // i32はCopyなので、この後にxを使っても
+                                    // 大丈夫
 
-} // Here, x goes out of scope, then s. But because s's value was moved, nothing
-  // special happens.
+} // ここでxがスコープを抜け、sもスコープを抜ける。ただし、sの値はムーブされているので、
+  // 何も特別なことは起こらない。
 
-fn takes_ownership(some_string: String) { // some_string comes into scope
+fn takes_ownership(some_string: String) { // some_stringがスコープに入る。
     println!("{}", some_string);
-} // Here, some_string goes out of scope and `drop` is called. The backing
-  // memory is freed.
+} // ここでsome_stringがスコープを抜け、`drop`が呼ばれる。後ろ盾してたメモリが解放される。
+  // 後ろ盾してたメモリが解放される。
 
-fn makes_copy(some_integer: i32) { // some_integer comes into scope
+fn makes_copy(some_integer: i32) { // some_integerがスコープに入る
     println!("{}", some_integer);
-} // Here, some_integer goes out of scope. Nothing special happens.
+} // ここでsome_integerがスコープを抜ける。何も特別なことはない。

listings/ch04-understanding-ownership/listing-04-04/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-04/src/main.rs

@@ -1,29 +1,25 @@
 fn main() {
-    let s1 = gives_ownership();         // gives_ownership moves its return
-                                        // value into s1
+    let s1 = gives_ownership();         // gives_ownershipは、戻り値をs1に
+                                        // ムーブする
 
-    let s2 = String::from("hello");     // s2 comes into scope
+    let s2 = String::from("hello");     // s2がスコープに入る
 
-    let s3 = takes_and_gives_back(s2);  // s2 is moved into
-                                        // takes_and_gives_back, which also
-                                        // moves its return value into s3
-} // Here, s3 goes out of scope and is dropped. s2 goes out of scope but was
-  // moved, so nothing happens. s1 goes out of scope and is dropped.
+    let s3 = takes_and_gives_back(s2);  // s2はtakes_and_gives_backにムーブされ
+                                        // 戻り値もs3にムーブされる
+} // ここで、s3はスコープを抜け、ドロップされる。s2もスコープを抜けるが、ムーブされているので、
+  // 何も起きない。s1もスコープを抜け、ドロップされる。
 
-fn gives_ownership() -> String {             // gives_ownership will move its
-                                             // return value into the function
-                                             // that calls it
+fn gives_ownership() -> String {             // gives_ownershipは、戻り値を
+                                             // 呼び出した関数にムーブする
 
-    let some_string = String::from("hello"); // some_string comes into scope
+    let some_string = String::from("hello"); // some_stringがスコープに入る
 
-    some_string                              // some_string is returned and
-                                             // moves out to the calling
-                                             // function
+    some_string                              // some_stringが返され、呼び出し元関数に
+                                             // ムーブされる
 }
 
-// takes_and_gives_back will take a String and return one
-fn takes_and_gives_back(a_string: String) -> String { // a_string comes into
-                                                      // scope
+// takes_and_gives_backは、Stringを一つ受け取り、返す。
+fn takes_and_gives_back(a_string: String) -> String { // a_stringがスコープに入る。
 
-    a_string  // a_string is returned and moves out to the calling function
+    a_string  // a_stringが返され、呼び出し元関数にムーブされる
 }

listings/ch04-understanding-ownership/listing-04-05/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-05/src/main.rs

@@ -3,11 +3,12 @@ fn main() {
 
     let (s2, len) = calculate_length(s1);
 
+    //'{}'の長さは、{}です
     println!("The length of '{}' is {}.", s2, len);
 }
 
 fn calculate_length(s: String) -> (String, usize) {
-    let length = s.len(); // len() returns the length of a String
+    let length = s.len(); // len()メソッドは、Stringの長さを返します
 
     (s, length)
 }

listings/ch04-understanding-ownership/listing-04-06/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-06/output.txt

@@ -1,16 +1,18 @@
 $ cargo run
    Compiling ownership v0.1.0 (file:///projects/ownership)
 error[E0596]: cannot borrow `*some_string` as mutable, as it is behind a `&` reference
+             (`*some_string`は`&`参照の背後にあるため、それを可変として借用することはできません)
  --> src/main.rs:8:5
   |
-7 | fn change(some_string: &String) {
-  |                        ------- help: consider changing this to be a mutable reference: `&mut std::string::String`
 8 |     some_string.push_str(", world");
   |     ^^^^^^^^^^^ `some_string` is a `&` reference, so the data it refers to cannot be borrowed as mutable
-
-error: aborting due to previous error
+  |                (`some_string`は`&`参照なので、それが指すデータを可変として借用することはできません)
+  |
+help: consider changing this to be a mutable reference
+     (これを可変参照に変更することを検討してください)
+  |
+7 | fn change(some_string: &mut String) {
+  |                         +++
 
 For more information about this error, try `rustc --explain E0596`.
-error: could not compile `ownership`.
-
-To learn more, run the command again with --verbose.
+error: could not compile `ownership` (bin "ownership") due to 1 previous error

listings/ch04-understanding-ownership/listing-04-07/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Carol (Nichols || Goulding) <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-08/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-09/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/listing-04-09/src/main.rs

@@ -16,14 +16,21 @@ fn first_word(s: &str) -> &str {
 fn main() {
     let my_string = String::from("hello world");
 
-    // first_word works on slices of `String`s
-    // first_wordは`String`のスライスに対して機能する
+    // `first_word` works on slices of `String`s, whether partial or whole
+    // `first_word`は`String`の全体または部分へのスライスに対して機能する
+    let word = first_word(&my_string[0..6]);
     let word = first_word(&my_string[..]);
+    // `first_word` also works on references to `String`s, which are equivalent
+    // to whole slices of `String`s
+    // `first_word`は`String`の参照に対しても機能する。この場合は
+    // `String`全体へのスライスと同等。
+    let word = first_word(&my_string);
 
     let my_string_literal = "hello world";
 
-    // first_word works on slices of string literals
-    // first_wordは文字列リテラルのスライスに対して機能する
+    // `first_word` works on slices of string literals, whether partial or whole
+    // `first_word`は文字列リテラルの全体または部分へのスライスに対して機能する
+    let word = first_word(&my_string_literal[0..6]);
     let word = first_word(&my_string_literal[..]);
 
     // Because string literals *are* string slices already,

listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/src/main.rs

@@ -2,8 +2,8 @@ fn main() {
     // ANCHOR: here
     let mut s = String::from("hello");
 
-    s.push_str(", world!"); // push_str() appends a literal to a String
+    s.push_str(", world!"); // push_str()関数は、リテラルをStringに付け加える
 
-    println!("{}", s); // This will print `hello, world!`
+    println!("{}", s); // これは`hello, world!`と出力する
                        // ANCHOR_END: here
 }

listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-02-string-scope/src/main.rs

@@ -1,10 +1,10 @@
 fn main() {
     // ANCHOR: here
-    {
-        let s = String::from("hello"); // s is valid from this point forward
+    {  
+        let s = String::from("hello"); // sはここから有効になる
 
-        // do stuff with s
-    }                                  // this scope is now over, and s is no
-                                       // longer valid
+        // sで作業をする
+    }                                  // このスコープはここでおしまい。sは
+                                       // もう有効ではない
     // ANCHOR_END: here
 }

listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/output.txt

@@ -1,19 +1,25 @@
 $ cargo run
    Compiling ownership v0.1.0 (file:///projects/ownership)
 error[E0382]: borrow of moved value: `s1`
+              (ムーブされた値の借用: `s1`)
  --> src/main.rs:5:28
   |
 2 |     let s1 = String::from("hello");
-  |         -- move occurs because `s1` has type `std::string::String`, which does not implement the `Copy` trait
+  |         -- move occurs because `s1` has type `String`, which does not implement the `Copy` trait
+  |            (`s1`は`String`型を持ち、これは`Copy`トレイトを実装していないので、ムーブが発生します)
 3 |     let s2 = s1;
   |              -- value moved here
-4 | 
+  |                 (ここで値がムーブされました)
+4 |
 5 |     println!("{}, world!", s1);
   |                            ^^ value borrowed here after move
-
-error: aborting due to previous error
+  |                               (ムーブ後にここで借用されています)
+  |
+  = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider cloning the value if the performance cost is acceptable
+  |
+3 |     let s2 = s1.clone();
+  |                ++++++++
 
 For more information about this error, try `rustc --explain E0382`.
-error: could not compile `ownership`.
-
-To learn more, run the command again with --verbose.
+error: could not compile `ownership` (bin "ownership") due to 1 previous error

listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs

@@ -6,6 +6,7 @@ fn main() {
     let len = calculate_length(&s1);
     // ANCHOR_END: here
 
+    // '{}'の長さは、{}です
     println!("The length of '{}' is {}.", s1, len);
 }
 

listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "ownership"
 version = "0.1.0"
-authors = ["Your Name <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs

@@ -7,8 +7,8 @@ fn main() {
 }
 
 // ANCHOR: here
-fn calculate_length(s: &String) -> usize { // s is a reference to a String
+fn calculate_length(s: &String) -> usize { // sはStringへの参照
     s.len()
-} // Here, s goes out of scope. But because it does not have ownership of what
-  // it refers to, nothing happens.
+} // ここで、sはスコープ外になる。けど、参照しているものの所有権を持っているわけではないので
+  // 何も起こらない
 // ANCHOR_END: here