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C++14 lambda 用法

 2 years ago
source link: https://forrestsu.github.io/posts/cpp/cpp14-lambda-usage/
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C++14 lambda 用法

2020年2月7日
| 字数 920
| CPP
| 阅读 36

1 嵌套lambda表达式

写一个lambda表达式A，其入参是一个lambda表达式B：

#include <cstdio>
#include <iostream>

namespace example01 {

template<typename Func>
void run_task(Func &&func) {
    int arg = 100;
    printf("1. arg >> %d\n", arg);
    /**
     * 定义一个别名,进行引用捕获
     * (注意：引用捕获时，请考虑被捕获对象的生命周期)
     */
    func([&i = arg]() mutable {
        ++i;
        printf("3. i == %d\n", i);
        throw std::logic_error("逻辑错误");
    });
    printf("6. arg << %d\n", arg);
}

inline void run() {
    //写一个lambda表达式A，其入参是一个lambda表达式B
    example01::run_task([](auto get_ex) {
        printf("2. start check\n");
        try {
            get_ex();
        } catch (std::exception &ex) {
            std::cout << "4. accept failed: " << ex.what() << "\n";
        }
        printf("5. end check\n");
    });
}
} //namespace example

int main() {
    example01::run();
    return 0;
}

输出结果如下:

  1. arg » 100
  2. start check
  3. i == 101
  4. accept failed: 逻辑错误
  5. end check
  6. arg « 101

当嵌套使用lambda表达式时，代码比较难读，代码书写的顺序和执行顺序差异很大！


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