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feat(cpp14): add 05-binary-literals
Book chapter (zh + en): - section 一/I: Basic usage — binary flags and bit masks - section 二/II: Real-world case — UTF-8 encoding masks from msvc-stl/stl/inc/format#L259-L267 - section 三/III: Notes — integer only, digit separator combination - section 四/IV: Exercise topics and d2x checker command - section 五/V: External resources Exercise: 0. Bit mask operations with binary literals. 3 D2X_YOUR_ANSWER. Build wiring: - register 05 target in dslings/cpp14, dslings/en/cpp14, solutions/cpp14 - add 05 entry to zh/en SUMMARY.md
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‎book/en/src/SUMMARY.md‎

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- [Generic Lambdas](./cpp14/00-generic-lambdas.md)
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- [Binary Literals](./cpp14/05-binary-literals.md)
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# Additional Resources
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- [Changelog](changelog.md)

‎book/en/src/cpp14/05-binary-literals.md‎

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<div align=right>
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🌎 [中文] | [English]
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</div>
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[中文]: ../../cpp14/05-binary-literals.html
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[English]: ./05-binary-literals.html
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# Binary Literals
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C++14 introduces the `0b` / `0B` prefix for binary integer literals, making bit-level values directly readable
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| Book | Video | Code | X |
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| --- | --- | --- | --- |
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| [cppreference-integer_literal](https://en.cppreference.com/w/cpp/language/integer_literal) / [markdown](https://github.com/mcpp-community/d2mcpp/blob/main/book/en/src/cpp14/05-binary-literals.md) | [Video Explanation]() | [Exercise Code](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/05-binary-literals-0.cpp) | |
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**Why introduced?**
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Bit masks and flag bits expressed in decimal or hex cannot directly convey the binary bit layout. `0b0010'1100` makes every bit's meaning visible at a glance
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## I. Basic Usage and Scenarios
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```cpp
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int a = 0b1010; // 10
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int b = 0B1111; // 15
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// Bit masks — binary representation is the most intuitive
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constexpr unsigned READ = 0b001;
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constexpr unsigned WRITE = 0b010;
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constexpr unsigned EXEC = 0b100;
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unsigned perm = 0b101; // READ | EXEC
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```
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## II. Real-World Case — Binary Literals in the STL
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> The MSVC STL uses binary literals for bit masks in Unicode handling. The example below cites the vendored [MSVC STL](https://github.com/mcpp-community/d2mcpp/tree/main/msvc-stl) (source: [`msvc-stl/stl/inc/format`](https://github.com/mcpp-community/d2mcpp/blob/main/msvc-stl/stl/inc/format#L259-L267))
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```cpp
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// MSVC STL · msvc-stl/stl/inc/format (abridged)
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// UTF-8 encoding — mask out the effective bits per byte count
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switch (_Num_bytes) {
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case 2:
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_Val &= 0b1'1111u; // 2 bytes: keep lower 5 bits
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break;
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case 3:
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_Val &= 0b1111u; // 3 bytes: keep lower 4 bits
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break;
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case 4:
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_Val &= 0b111u; // 4 bytes: keep lower 3 bits
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}
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```
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## III. Notes
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- Binary literals can only be used with integer types
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- Can be combined with digit separators: `0b1010'1100`
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- Both `0b` and `0B` work; `0b` is more common
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## IV. Exercise Code
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### Exercise Topics
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- 0 - [Binary Literals — Bit Mask Operations](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/05-binary-literals-0.cpp)
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### Auto-Checker Command
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```
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d2x checker binary-literals
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```
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## V. Other
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- [Discussion Forum](https://forum.d2learn.org/category/20)
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- [d2mcpp Tutorial Repository](https://github.com/mcpp-community/d2mcpp)
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- [Tutorial Video List](https://space.bilibili.com/65858958/lists/5208246)
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- [Tutorial Support Tool - xlings](https://github.com/openxlings/xlings)

‎book/src/SUMMARY.md‎

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- [泛型 lambda - generic lambdas](./cpp14/00-generic-lambdas.md)
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- [二进制字面量 - binary literals](./cpp14/05-binary-literals.md)
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# 其他
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- [更新日志](changelog.md)

‎book/src/cpp14/05-binary-literals.md‎

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<div align=right>
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🌎 [中文] | [English]
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</div>
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[中文]: ./05-binary-literals.html
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[English]: ../en/cpp14/05-binary-literals.html
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# 二进制字面量 - binary literals
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C++14 引入 `0b` / `0B` 前缀表示二进制字面量, 让位运算和底层编程中的数值表示更加直观
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| Book | Video | Code | X |
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| --- | --- | --- | --- |
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| [cppreference-integer_literal](https://en.cppreference.com/w/cpp/language/integer_literal) / [markdown](https://github.com/mcpp-community/d2mcpp/blob/main/book/src/cpp14/05-binary-literals.md) | [视频解读]() | [练习代码](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/05-binary-literals-0.cpp) | |
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**为什么引入?**
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位掩码和标志位用十进制或十六进制表示时, 无法直接对应二进制位布局。`0b0010'1100` 让每一位的含义肉眼可见
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## 一、基础用法和场景
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```cpp
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int a = 0b1010; // 10
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int b = 0B1111; // 15
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// 位掩码 — 二进制表示最直观
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constexpr unsigned READ = 0b001;
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constexpr unsigned WRITE = 0b010;
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constexpr unsigned EXEC = 0b100;
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unsigned perm = 0b101; // READ | EXEC
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```
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## 二、真实案例 - STL 中的二进制字面量
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> MSVC STL 在 Unicode 处理中使用二进制字面量表示位掩码, 配合数字分隔符更加清晰。下面以仓库内置的 [MSVC STL](https://github.com/mcpp-community/d2mcpp/tree/main/msvc-stl) 为例 (源码: [`msvc-stl/stl/inc/format`](https://github.com/mcpp-community/d2mcpp/blob/main/msvc-stl/stl/inc/format#L259-L267))
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```cpp
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// MSVC STL · msvc-stl/stl/inc/format (有删节)
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// UTF-8 编码 — 按字节数截取有效位
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switch (_Num_bytes) {
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case 2:
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_Val &= 0b1'1111u; // 2 字节: 取低 5 位
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break;
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case 3:
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_Val &= 0b1111u; // 3 字节: 取低 4 位
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break;
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case 4:
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_Val &= 0b111u; // 4 字节: 取低 3 位
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}
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```
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UTF-8 编码中不同长度字符的有效数据位数不同 (5/4/3 位), 二进制字面量让每一位掩码都对应文档规范中的位布局, 十进制 `31` / `15` / `7` 则完全丢失这层语义
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## 三、注意事项
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- 二进制字面量只能用于整数类型
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- 可以和数字分隔符组合: `0b1010'1100`
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- 前缀大小写均可, 推荐 `0b` (更常见)
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## 四、练习代码
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### 练习代码主题
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- 0 - [二进制字面量 — 位掩码运算](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/05-binary-literals-0.cpp)
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### 练习代码自动检测命令
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```
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d2x checker binary-literals
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```
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## 五、其他
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- [交流讨论](https://forum.d2learn.org/category/20)
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- [d2mcpp教程仓库](https://github.com/mcpp-community/d2mcpp)
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- [教程视频列表](https://space.bilibili.com/65858958/lists/5208246)
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- [教程支持工具-xlings](https://github.com/openxlings/xlings)

‎dslings/cpp14/05-binary-literals-0.cpp‎

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// d2mcpp: https://github.com/mcpp-community/d2mcpp
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// license: Apache-2.0
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// file: dslings/cpp14/05-binary-literals-0.cpp
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//
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// Exercise/练习: cpp14 | 05 - binary literals | 二进制字面量位掩码
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//
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// Tips/提示:
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// - 0b / 0B 前缀表示二进制字面量
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// - 位掩码用二进制表示最直观
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//
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// Docs/文档:
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// - https://en.cppreference.com/w/cpp/language/integer_literal
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// - https://github.com/mcpp-community/d2mcpp/blob/main/book/src/cpp14/05-binary-literals.md
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//
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// 练习交流讨论: http://forum.d2learn.org/category/20
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//
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// Auto-Checker/自动检测命令:
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//
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// d2x checker binary-literals
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//
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#include <d2x/cpp/common.hpp>
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constexpr unsigned READ = 0b001;
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constexpr unsigned WRITE = D2X_YOUR_ANSWER;
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constexpr unsigned EXEC = 0b100;
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bool has_perm(unsigned perm, unsigned flag) { return perm & flag; }
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int main() {
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unsigned p1 = 0b101;
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d2x_assert(has_perm(p1, READ));
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d2x_assert(!has_perm(p1, WRITE));
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d2x_assert(has_perm(p1, EXEC));
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unsigned p2 = D2X_YOUR_ANSWER;
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d2x_assert(has_perm(p2, READ));
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d2x_assert(has_perm(p2, WRITE));
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d2x_assert(has_perm(p2, EXEC));
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d2x_assert_eq(0b1111, D2X_YOUR_ANSWER);
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D2X_WAIT
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return 0;
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}

‎dslings/cpp14/xmake.lua‎

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target("cpp14-00-generic-lambdas-1")
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set_kind("binary")
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add_files("00-generic-lambdas-1.cpp")
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-- target: cpp14-05-binary-literals
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target("cpp14-05-binary-literals-0")
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set_kind("binary")
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add_files("05-binary-literals-0.cpp")

‎dslings/en/cpp14/05-binary-literals-0.cpp‎

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// d2mcpp: https://github.com/mcpp-community/d2mcpp
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// license: Apache-2.0
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// file: dslings/en/cpp14/05-binary-literals-0.cpp
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//
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// Exercise: cpp14 | 05 - binary literals | bit mask operations
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//
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// Tips:
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// - 0b / 0B prefix for binary integer literals
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// - Bit masks are most intuitive in binary form
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//
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// Docs:
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// - https://en.cppreference.com/w/cpp/language/integer_literal
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// - https://github.com/mcpp-community/d2mcpp/blob/main/book/en/src/cpp14/05-binary-literals.md
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//
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// Discussion Forum: http://forum.d2learn.org/category/20
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//
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// Auto-Checker:
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//
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// d2x checker binary-literals
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//
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#include <d2x/cpp/common.hpp>
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constexpr unsigned READ = 0b001;
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constexpr unsigned WRITE = D2X_YOUR_ANSWER;
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constexpr unsigned EXEC = 0b100;
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bool has_perm(unsigned perm, unsigned flag) { return perm & flag; }
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int main() {
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unsigned p1 = 0b101;
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d2x_assert(has_perm(p1, READ));
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d2x_assert(!has_perm(p1, WRITE));
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d2x_assert(has_perm(p1, EXEC));
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unsigned p2 = D2X_YOUR_ANSWER;
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d2x_assert(has_perm(p2, READ));
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d2x_assert(has_perm(p2, WRITE));
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d2x_assert(has_perm(p2, EXEC));
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d2x_assert_eq(0b1111, D2X_YOUR_ANSWER);
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D2X_WAIT
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return 0;
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}

‎dslings/en/cpp14/xmake.lua‎

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target("cpp14-00-generic-lambdas-1")
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set_kind("binary")
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add_files("00-generic-lambdas-1.cpp")
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-- target: cpp14-05-binary-literals
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target("cpp14-05-binary-literals-0")
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set_kind("binary")
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add_files("05-binary-literals-0.cpp")

‎solutions/cpp14/05-binary-literals-0.cpp‎

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// d2mcpp: https://github.com/mcpp-community/d2mcpp
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// license: Apache-2.0
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// reference solution for: dslings/cpp14/05-binary-literals-0.cpp
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//
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// 用途: 仅给 CI 与维护者参考使用，不是教程入口。
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// 教程练习入口: dslings/cpp14/05-binary-literals-0.cpp
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//
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#include <d2x/cpp/common.hpp>
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constexpr unsigned READ = 0b001;
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constexpr unsigned WRITE = 0b010;
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constexpr unsigned EXEC = 0b100;
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bool has_perm(unsigned perm, unsigned flag) { return perm & flag; }
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int main() {
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unsigned p1 = 0b101;
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d2x_assert(has_perm(p1, READ));
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d2x_assert(!has_perm(p1, WRITE));
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d2x_assert(has_perm(p1, EXEC));
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unsigned p2 = 0b111;
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d2x_assert(has_perm(p2, READ));
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d2x_assert(has_perm(p2, WRITE));
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d2x_assert(has_perm(p2, EXEC));
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d2x_assert_eq(0b1111, 15);
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return 0;
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}

‎solutions/cpp14/xmake.lua‎

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target("cpp14-00-generic-lambdas-1-ref")
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set_kind("binary")
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add_files("00-generic-lambdas-1.cpp")
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-- target: cpp14-05-binary-literals
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target("cpp14-05-binary-literals-0-ref")
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set_kind("binary")
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add_files("05-binary-literals-0.cpp")

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