Can Lambda expression be downgraded to C++ 98

Question

I recently got a problem need to integrate C++ 11 code written with lambda expression to old code base which only support C++ 98 compiler. I figured out couple of possible equiv

Answer 1

With Functor:

struct Functor
{
    explicit Functor(uint attributes) : attributes(attributes) {}
    void operator () (uint index, void * objectAddress) const
    {
        if ((ObjectInfo(index) & attributes) != 0)
        {
            fn(index, objectAddress);
        }
    }
    uint attributes;
};

And then call

uint attributes = 0x0030;
// ....
ForEachObject(Functor(attributes));

For each different lambda, you have to write a functor. You don't have to modify ForEachObject

Answer 2

Can Lamda expression be downgrade to C++ 98

No they cannot. Prior C++11 standards have no notion of lambda syntax.

Though there are surrogates available like boost::lambda

You can provide functor style classes, overriding the call operator (<return_type> operator()(<args>);), to provide the same effect, as mentioned in the other answer.