Merge pull request #99 from dalance/borrow-and-asref

5.10. Borrow and AsRef

Author: tatsuya6502

1.6/ja/book/borrow-and-asref.md

@@ -1,17 +1,22 @@
-% Borrow and AsRef
+% BorrowとAsRef
+<!-- % Borrow and AsRef -->
 
-The [`Borrow`][borrow] and [`AsRef`][asref] traits are very similar, but
-different. Here’s a quick refresher on what these two traits mean.
+<!-- The [`Borrow`][borrow] and [`AsRef`][asref] traits are very similar, but -->
+<!-- different. Here’s a quick refresher on what these two traits mean. -->
+[`Borrow`][borrow] トレイトと [`AsRef`][asref] トレイトはとてもよく似ていますが違うものです。ここでは2つのトレイトの意味を簡単に説明します。
 
 [borrow]: ../std/borrow/trait.Borrow.html
 [asref]: ../std/convert/trait.AsRef.html
 
+<!-- # Borrow -->
 # Borrow
 
-The `Borrow` trait is used when you’re writing a datastructure, and you want to
-use either an owned or borrowed type as synonymous for some purpose.
+<!-- The `Borrow` trait is used when you’re writing a datastructure, and you want to -->
+<!-- use either an owned or borrowed type as synonymous for some purpose. -->
+`Borrow` トレイトはデータ構造を書いていて、所有型と借用型を同等に扱いたいときに使います。
 
-For example, [`HashMap`][hashmap] has a [`get` method][get] which uses `Borrow`:
+<!-- For example, [`HashMap`][hashmap] has a [`get` method][get] which uses `Borrow`: -->
+例えば、 [`HashMap`][hashmap] には `Borrow` を使った [`get` メソッド][get] があります。
 
 ```rust,ignore
 fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
@@ -22,17 +27,19 @@ fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
 [hashmap]: ../std/collections/struct.HashMap.html
 [get]: ../std/collections/struct.HashMap.html#method.get
 
-This signature is pretty complicated. The `K` parameter is what we’re interested
-in here. It refers to a parameter of the `HashMap` itself:
+<!-- This signature is pretty complicated. The `K` parameter is what we’re interested -->
+<!-- in here. It refers to a parameter of the `HashMap` itself: -->
+このシグネチャは少し複雑です。`K` パラメータに注目してください。これは以下のように `HashMap` 自身のパラメータになっています。
 
 ```rust,ignore
 struct HashMap<K, V, S = RandomState> {
 ```
 
-The `K` parameter is the type of _key_ the `HashMap` uses. So, looking at
-the signature of `get()` again, we can use `get()` when the key implements
-`Borrow<Q>`. That way, we can make a `HashMap` which uses `String` keys,
-but use `&str`s when we’re searching:
+<!-- The `K` parameter is the type of _key_ the `HashMap` uses. So, looking at -->
+<!-- the signature of `get()` again, we can use `get()` when the key implements -->
+<!-- `Borrow<Q>`. That way, we can make a `HashMap` which uses `String` keys, -->
+<!-- but use `&str`s when we’re searching: -->
+`K` パラメータは `HashMap` の「キー」を表す型です。ここで再び `get()` のシグネチャを見ると、キーが `Borrow<Q>` を実装しているときに `get()` を使えることが分かります。そのため、以下のように `String` をキーとした `HashMap` を検索するときに `&str` を使うことができます。
 
 ```rust
 use std::collections::HashMap;
@@ -43,13 +50,15 @@ map.insert("Foo".to_string(), 42);
 assert_eq!(map.get("Foo"), Some(&42));
 ```
 
-This is because the standard library has `impl Borrow<str> for String`.
+<!-- This is because the standard library has `impl Borrow<str> for String`. -->
+これは標準ライブラリが `impl Borrow<str> for String` を提供しているためです。
 
-For most types, when you want to take an owned or borrowed type, a `&T` is
-enough. But one area where `Borrow` is effective is when there’s more than one
-kind of borrowed value. This is especially true of references and slices: you
-can have both an `&T` or a `&mut T`. If we wanted to accept both of these types,
-`Borrow` is up for it:
+<!-- For most types, when you want to take an owned or borrowed type, a `&T` is -->
+<!-- enough. But one area where `Borrow` is effective is when there’s more than one -->
+<!-- kind of borrowed value. This is especially true of references and slices: you -->
+<!-- can have both an `&T` or a `&mut T`. If we wanted to accept both of these types, -->
+<!-- `Borrow` is up for it: -->
+所有型か借用型のどちらかを取りたい場合、たいていは `&T` で十分ですが、借用された値が複数種類ある場合 `Borrow` が役に立ちます。特に参照とスライスは `&T` と `&mut T` のいずれも取りうるため、そのどちらも受け入れたい場合は `Borrow` がよいでしょう。
 
 ```rust
 use std::borrow::Borrow;
@@ -65,12 +74,15 @@ foo(&i);
 foo(&mut i);
 ```
 
-This will print out `a is borrowed: 5` twice.
+<!-- This will print out `a is borrowed: 5` twice. -->
+上のコードは `a is borrowed: 5` を二度出力します。
 
+<!-- # AsRef -->
 # AsRef
 
-The `AsRef` trait is a conversion trait. It’s used for converting some value to
-a reference in generic code. Like this:
+<!-- The `AsRef` trait is a conversion trait. It’s used for converting some value to -->
+<!-- a reference in generic code. Like this: -->
+`AsRef` トレイトは変換用のトレイトです。ジェネリックなコードにおいて、値を参照に変換したい場合に使います。
 
 ```rust
 let s = "Hello".to_string();
@@ -80,14 +92,18 @@ fn foo<T: AsRef<str>>(s: T) {
 }
 ```
 
-# Which should I use?
+<!-- # Which should I use? -->
+# どちらを使うべきか
 
-We can see how they’re kind of the same: they both deal with owned and borrowed
-versions of some type. However, they’re a bit different.
+<!-- We can see how they’re kind of the same: they both deal with owned and borrowed -->
+<!-- versions of some type. However, they’re a bit different. -->
+ここまでで見てきた通り、2つのトレイトは、どちらもある型の所有型バージョンと借用型バージョンの両方を扱う、という意味で同じような種類のものですが、少し違います。
 
-Choose `Borrow` when you want to abstract over different kinds of borrowing, or
-when you’re building a datastructure that treats owned and borrowed values in
-equivalent ways, such as hashing and comparison.
+<!-- Choose `Borrow` when you want to abstract over different kinds of borrowing, or -->
+<!-- when you’re building a datastructure that treats owned and borrowed values in -->
+<!-- equivalent ways, such as hashing and comparison. -->
+いくつかの異なる種類の借用を抽象化したい場合や、ハッシュ化や比較のために所有型と借用型を同等に扱いたいデータ構造を作る場合は `Borrow` を使ってください。
 
-Choose `AsRef` when you want to convert something to a reference directly, and
-you’re writing generic code.
+<!-- Choose `AsRef` when you want to convert something to a reference directly, and -->
+<!-- you’re writing generic code. -->
+ジェネリックなコードで値を参照に直接変換したい場合は `AsRef` を使ってください。

TranslationTable.md

@@ -88,6 +88,7 @@
 | interpolate                    | インターポーレートする
 | interpolation                  | インターポーレーション
 | Intrinsics                     | Intrinsic
+| key                            | キー
 | keyword                        | キーワード
 | Lang Items                     | Lang Item
 | leak                           | リーク
@@ -116,6 +117,7 @@
 | owner                          | 所有者
 | ownership                      | 所有権
 | panic                          | パニック
+| parameter                      | パラメータ
 | parametric polymorphism        | パラメトリック多相
 | parse                          | パース、パースする
 | patch                          | パッチ