commit 393248401b9f3e65908d62a6a02b345c8b5cc8b9
parent 66196ec302f9683ed2178397f7a5135d37f23300
Author: Shimmy Xu <shimmy.xu@shimmy1996.com>
Date: Wed, 3 Jul 2019 20:21:29 -0500
Add Chinese Translation for enumerate() with C++
Diffstat:
3 files changed, 146 insertions(+), 2 deletions(-)
diff --git a/content/posts/2019-04-27-enumerate-with-c-plus-plus.en.md b/content/posts/2019-04-27-enumerate-with-c-plus-plus.en.md
@@ -34,7 +34,7 @@ std::for_each(v.begin(), v.end(),
});
```
-This could be used with all the algorithms that guarantees in-order application of the lambda, but I don't like the dangling `i++` that could get mixed up with other logic.
+This could be used with all the algorithms that guarantees in-order application of the lambda, but I don't like the dangling `++i` that could get mixed up with other logic.
The second way utilizes structured binding in for loops:
diff --git a/content/posts/2019-04-27-enumerate-with-c-plus-plus.zh.md b/content/posts/2019-04-27-enumerate-with-c-plus-plus.zh.md
@@ -0,0 +1,79 @@
++++
+title = "用 C++ 来 enumerate()"
+tags = ["c-plus-plus"]
+categories = ["programming"]
+draft = false
+date = 2019-04-27
+slug = "enumerate-with-c-plus-plus"
++++
+
+不少编程语言都提供了在迭代容器的同时记录步数的方法，例如 Python 的 `enumerate()` ：
+
+```python
+for i, elem in enumerate(v):
+ print(i, elem)
+```
+
+以及 Rust 里 `std::iter::Iterator` 特性下的 `enumerate()` ：
+
+```rust
+for (i, elem) in v.iter().enumerate() {
+ println!("{}, {}", i, elem);
+}
+```
+
+这里记录了如何在 C++17 或更新的标准里尽量简洁地实现类似功能的办法。
+
+第一种方法是使用一个可变的 lambda ：
+
+```c++
+std::for_each(v.begin(), v.end(),
+ [i = 0](auto elem) mutable {
+ std::cout << i << ", " << elem << std::endl;
+ ++i;
+ });
+```
+
+这个方法使用于所有能够保证 lambda 有序执行的算法，但是我并不喜欢末尾很可能被混入其他逻辑的 `++i` 。
+
+第二种方法是在 for 循环中使用结构化绑定：
+
+```c++
+for (auto [i, elem_it] = std::tuple{0, v.begin()}; elem_it != v.end();
+ ++i, ++elem_it) {
+ std::cout << i << ", " << *elem_it << std::endl;
+}
+```
+
+为了不让编译器默认创建只允许同种内容的 `std::initializer_list` ，我们必须加上 `std::tuple` 。
+
+第三种最朴实无华的办法是在循环的每一步计算指针距离：
+
+```c++
+for (auto elem_it = v.begin(); elem_it != v.end(); ++elem_it) {
+ auto i = std::distance(v.begin(), elem_it);
+ std::cout << i << ", " << *elem_it << std::endl;
+}
+```
+
+由于这种方法需要我们在两个地方指定初始指针，我更喜欢之前提到的基于计数器的方法。
+
+在 C++20 中，我们可以在基于范围的 for 循环中加入初始化语句：
+
+```c++
+for (auto i = 0; auto elem : v) {
+ std::cout << i << ", " << elem << std::endl;
+ i++;
+}
+```
+
+新加入的 `<ranges>` 库则提供了一种更加吸引人的实现方法：
+
+```c++
+for (auto [i, elem] : v | std::view::transform(
+ [i = 0](auto elem) mutable { return std::tuple{i++, elem}; })) {
+ std::cout << i << ", " << elem << std::endl;
+}
+```
+
+我最喜欢基于结构化绑定和 `<ranges>` 库的方法。当然如果要是有 `std::view::enumerate` 来一劳永逸地解决这个问题就最好不过了。
diff --git a/org/2019.org b/org/2019.org
@@ -145,7 +145,7 @@ The first way is to use a mutable lambda:
++i;
});
#+END_SRC
-This could be used with all the algorithms that guarantees in-order application of the lambda, but I don't like the dangling =i++= that could get mixed up with other logic.
+This could be used with all the algorithms that guarantees in-order application of the lambda, but I don't like the dangling =++i= that could get mixed up with other logic.
The second way utilizes structured binding in for loops:
#+BEGIN_SRC c++
@@ -182,6 +182,71 @@ Meh, not that impressive. The new =<ranges>= library provides a more appealing w
I like the structured binding method and the =<ranges>= based method the most. It would be even better though if we can get a =std::view::enumerate= to solve this problem once and for all.
+*** DONE zh
+:PROPERTIES:
+:EXPORT_TITLE: 用 C++ 来 enumerate()
+:EXPORT_FILE_NAME: 2019-04-27-enumerate-with-c-plus-plus.zh.md
+:END:
+
+不少编程语言都提供了在迭代容器的同时记录步数的方法，例如 Python 的 =enumerate()= ：
+#+BEGIN_SRC python
+ for i, elem in enumerate(v):
+ print(i, elem)
+#+END_SRC
+以及 Rust 里 =std::iter::Iterator= 特性下的 =enumerate()= ：
+#+BEGIN_SRC rust
+ for (i, elem) in v.iter().enumerate() {
+ println!("{}, {}", i, elem);
+ }
+#+END_SRC
+这里记录了如何在 C++17 或更新的标准里尽量简洁地实现类似功能的办法。
+
+
+第一种方法是使用一个可变的 lambda ：
+#+BEGIN_SRC c++
+ std::for_each(v.begin(), v.end(),
+ [i = 0](auto elem) mutable {
+ std::cout << i << ", " << elem << std::endl;
+ ++i;
+ });
+#+END_SRC
+这个方法使用于所有能够保证 lambda 有序执行的算法，但是我并不喜欢末尾很可能被混入其他逻辑的 =++i= 。
+
+第二种方法是在 for 循环中使用结构化绑定：
+#+BEGIN_SRC c++
+ for (auto [i, elem_it] = std::tuple{0, v.begin()}; elem_it != v.end();
+ ++i, ++elem_it) {
+ std::cout << i << ", " << *elem_it << std::endl;
+ }
+#+END_SRC
+为了不让编译器默认创建只允许同种内容的 =std::initializer_list= ，我们必须加上 =std::tuple= 。
+
+第三种最朴实无华的办法是在循环的每一步计算指针距离：
+#+BEGIN_SRC c++
+ for (auto elem_it = v.begin(); elem_it != v.end(); ++elem_it) {
+ auto i = std::distance(v.begin(), elem_it);
+ std::cout << i << ", " << *elem_it << std::endl;
+ }
+#+END_SRC
+由于这种方法需要我们在两个地方指定初始指针，我更喜欢之前提到的基于计数器的方法。
+
+在 C++20 中，我们可以在基于范围的 for 循环中加入初始化语句：
+#+BEGIN_SRC c++
+ for (auto i = 0; auto elem : v) {
+ std::cout << i << ", " << elem << std::endl;
+ i++;
+ }
+#+END_SRC
+新加入的 =<ranges>= 库则提供了一种更加吸引人的实现方法：
+#+BEGIN_SRC c++
+ for (auto [i, elem] : v | std::view::transform(
+ [i = 0](auto elem) mutable { return std::tuple{i++, elem}; })) {
+ std::cout << i << ", " << elem << std::endl;
+ }
+#+END_SRC
+
+我最喜欢基于结构化绑定和 =<ranges>= 库的方法。当然如果要是有 =std::view::enumerate= 来一劳永逸地解决这个问题就最好不过了。
+
* Geekery :@geekery:
** TODO Installing Gentoo :linux:
:PROPERTIES: