关于编译Lambda时报告返回的为void的错误

这个错误的信息是这样的：

a lambda that has been specified to have a void return type cannot return a value

报告错误的lambda的写法大概是这样：

[] (int a, int b){
    if (a<b)
        return true;
    else
        return false;
};

这个lambda在gcc下编译没有问题，在vc10下就会报上面的那个错误。

可以换成这种写法就OK了。

[](int a, int b){
    return a<b;
};

至于为什么，看这个解释：

The C++11 standard, §5.1.2/4 states:

If a lambda-expression does not include a trailing-return-type, it is as if the trailing-return-type denotes the following type:

• If the compound-statement is of the form { return expression ; } the type of the returned expression after lvalue-to-rvalue conversion (4.1), array-to-pointer conversion (4.2), and function-to-pointer conversion (4.3);

• otherwise, void.