Comparison define in C++

Asked Aug 19 '16 at 05:20

Active Aug 19 '16 at 05:20

Viewed 52 times

Got a problem when reviewing other's code in C++. He defines a comparison as the following code:

auto f = [](const pair<Tweet*, Tweet*>& x, const pair<Tweet*, Tweet*>& y) {
        return x.second->time < y.second->time;
};

The environment is the follow:(h is defined as vector<pair<Tweet*, Tweet*>> h;)

make_heap(h.begin(), h.end(), f);

My question:

I trying to rewrite as follow but does not work properly, what do I miss?

bool f(const pair<Tweet*, Tweet*>& x, const pair<Tweet*, Tweet*>& y)
{
  return x.second->time < y.second->time;
}

asked Aug 19 '16 at 05:20

Junsu Fred Shen

2

Read about [lambdas](http://en.cppreference.com/w/cpp/language/lambda). – Some programmer dude Aug 19 '16 at 05:23
What doesn't work properly? There's no error, nor an actual [mcve] that we can refer to. If I had to guess, I would say that the error is something like *function definition is not allowed here*. – chris Aug 19 '16 at 05:23
@Joachim Pileborg: thanks, I will read through. – Junsu Fred Shen Aug 19 '16 at 05:28
@chris: the comparison does not return the correct output. I will edit my answer and add the sample idea – Junsu Fred Shen Aug 19 '16 at 05:28

0 Answers0