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feat(cpp14): add 06-digit-separators
Book chapter (zh + en): - section 一/I: Basic usage — decimal, hex, binary with separators - section 二/II: Real-world case — UTF-8 continuation byte mask 0b11'1111u from msvc-stl/stl/inc/format#L281-L282 - section 三/III: Notes — start/end/consecutive restrictions - section 四/IV: Exercise topics and d2x checker command - section 五/V: External resources Exercise: 0. Digit separators in decimal, hex, and binary. 3 D2X_YOUR_ANSWER. Build wiring: - register 06 target in dslings/cpp14, dslings/en/cpp14, solutions/cpp14 - add 06 entry to zh/en SUMMARY.md
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‎book/en/src/SUMMARY.md‎

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# C++14 Core Language Features
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- [Generic Lambdas](./cpp14/00-generic-lambdas.md)
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- [Digit Separators](./cpp14/06-digit-separators.md)
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# Additional Resources
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‎book/en/src/cpp14/06-digit-separators.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]: ../../cpp14/06-digit-separators.html
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[English]: ./06-digit-separators.html
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# Digit Separators
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C++14 allows single quotes `'` as separators in numeric literals, improving readability without affecting the value
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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/cpp14/06-digit-separators.md) | [Video Explanation]() | [Exercise Code](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/06-digit-separators-0.cpp) | |
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**Why introduced?**
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`1000000000` is hard to parse, `0xFFFF0000` requires counting Fs. `1'000'000'000` and `0xFFFF'0000` make the numeric structure clear at a glance
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## I. Basic Usage and Scenarios
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```cpp
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int million = 1'000'000; // decimal
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int hex_val = 0xFF'FF'00'00; // hexadecimal
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int bin_val = 0b1010'1100'1111; // binary + separator
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static_assert(million == 1000000, "");
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```
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## II. Real-World Case — Digit Separators in the STL
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> The MSVC STL uses binary literals with digit separators in UTF-8 decoding. 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#L281-L282))
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```cpp
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// MSVC STL · msvc-stl/stl/inc/format (abridged)
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// UTF-8 decoding — extract the lower 6 bits of each continuation byte
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_Val = (_Val << 6) | (static_cast<unsigned char>(_First[_Idx]) & 0b11'1111u);
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```
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`0b11'1111u` is 63, and the `'` separator makes the binary mask's semantics directly visible in the literal — no mental conversion from `0x3F` or `63`
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## III. Notes
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- Cannot appear at the start or end: `'0` / `1'` are invalid
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- Cannot be consecutive: `1''0` is invalid
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- Does not affect the value, only improves readability
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## IV. Exercise Code
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### Exercise Topics
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- 0 - [Digit Separators — Large Numbers and Radix Combinations](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/06-digit-separators-0.cpp)
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### Auto-Checker Command
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```
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d2x checker digit-separators
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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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# C++14核心语言特性
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- [泛型 lambda - generic lambdas](./cpp14/00-generic-lambdas.md)
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- [数字分隔符 - digit separators](./cpp14/06-digit-separators.md)
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# 其他
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‎book/src/cpp14/06-digit-separators.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]: ./06-digit-separators.html
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[English]: ../en/cpp14/06-digit-separators.html
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# 数字分隔符 - digit separators
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C++14 允许在数字字面量中使用单引号 `'` 作为分隔符, 不影响数值, 显著提升大数可读性
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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/cpp14/06-digit-separators.md) | [视频解读]() | [练习代码](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/06-digit-separators-0.cpp) | |
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**为什么引入?**
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`1000000000` 很难分清位数, `0xFFFF0000` 需要仔细数几位 F。`1'000'000'000` 和 `0xFFFF'0000` 让数值结构一目了然
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## 一、基础用法和场景
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```cpp
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int million = 1'000'000; // 十进制
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int hex_val = 0xFF'FF'00'00; // 十六进制
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int bin_val = 0b1010'1100'1111; // 二进制 + 分隔符
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static_assert(million == 1000000, "");
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```
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分隔符可以出现在数字中任意位置, 不限制分组位数
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## 二、真实案例 - STL 中的数字分隔符
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> MSVC STL 在 UTF-8 解码中使用二进制字面量配合数字分隔符。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#L281-L282))
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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 解码 — 提取连续字节的低 6 位
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_Val = (_Val << 6) | (static_cast<unsigned char>(_First[_Idx]) & 0b11'1111u);
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```
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`0b11'1111u` 是 63, 用 `'` 将高位和低位分开后, 二进制掩码的语义直接从字面量可见, 无需心算 `0x3F` 或 `63`
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## 三、注意事项
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- 不能出现在数字开头或结尾: `'0` / `1'` 非法
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- 不能连续: `1''0` 非法
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- 不影响数值, 仅增强可读性
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## 四、练习代码
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### 练习代码主题
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- 0 - [数字分隔符 — 大数与进制组合](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/06-digit-separators-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 digit-separators
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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/cpp14/06-digit-separators-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/cpp14/06-digit-separators-0.cpp
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//
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// Exercise/练习: cpp14 | 06 - digit separators | 数字分隔符
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//
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// Tips/提示:
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// - 单引号 ' 分隔数字, 不影响数值
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// - 可用于十进制、十六进制、二进制字面量
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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/cpp14/06-digit-separators.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 digit-separators
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//
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#include <d2x/cpp/common.hpp>
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int main() {
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int million = 1'D2X_YOUR_ANSWER'000;
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d2x_assert_eq(million, 1000000);
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int hex_color = 0xFF'D2X_YOUR_ANSWER'BB;
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d2x_assert_eq(hex_color, 0xFFAABB);
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int bin_val = 0b1010'D2X_YOUR_ANSWER;
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d2x_assert_eq(bin_val, 0b10101100);
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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: cpp14-06-digit-separators
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target("cpp14-06-digit-separators-0")
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set_kind("binary")
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add_files("06-digit-separators-0.cpp")

‎dslings/en/cpp14/06-digit-separators-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/cpp14/06-digit-separators-0.cpp
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//
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// Exercise: cpp14 | 06 - digit separators
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//
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// Tips:
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// - Single quotes ' separate digits without affecting the value
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// - Works with decimal, hex, and binary literals
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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/cpp14/06-digit-separators.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 digit-separators
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//
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#include <d2x/cpp/common.hpp>
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int main() {
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int million = 1'D2X_YOUR_ANSWER'000;
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d2x_assert_eq(million, 1000000);
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int hex_color = 0xFF'D2X_YOUR_ANSWER'BB;
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d2x_assert_eq(hex_color, 0xFFAABB);
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int bin_val = 0b1010'D2X_YOUR_ANSWER;
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d2x_assert_eq(bin_val, 0b10101100);
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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: cpp14-06-digit-separators
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target("cpp14-06-digit-separators-0")
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set_kind("binary")
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add_files("06-digit-separators-0.cpp")

‎solutions/cpp14/06-digit-separators-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/cpp14/06-digit-separators-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/cpp14/06-digit-separators-0.cpp
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//
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#include <d2x/cpp/common.hpp>
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int main() {
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int million = 1'000'000;
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d2x_assert_eq(million, 1000000);
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int hex_color = 0xFF'AA'BB;
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d2x_assert_eq(hex_color, 0xFFAABB);
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int bin_val = 0b1010'1100;
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d2x_assert_eq(bin_val, 0b10101100);
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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: cpp14-06-digit-separators
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target("cpp14-06-digit-separators-0-ref")
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set_kind("binary")
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add_files("06-digit-separators-0.cpp")

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