为什么 lambda 返回 bool?

2022-01-19 00:00:00 return qt c++ return-type c++11

我已经开始学习 C++11 和 C++14，我有一个问题.为什么 lambda 不返回 23?

I've started learning C++11 and C++14 and i have a question. Why lambda not returns 23?

template<class T>
auto func(T t)
{
    return t;
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    auto abc = []()->auto { return func(23); };
    qDebug() << abc; // output: true

    return a.exec();
}

推荐答案

你需要真正执行 lambda:

You need to actually execute the lambda:

qDebug() << abc();

当前 << 重载正在将 lambda 的 type 转换为 bool，并输出.

Currently the << overload is converting the type of the lambda to a bool, and outputting that.

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