std::min_element on list does not return the minimum

Question

I have a while loop that initialize a list with some doubles.

I would like to output the smallest value but what I have done so far seem not be working, because I don't get any output.

This is the relevant part of my code:

    list<double> allDistances;

    std::ifstream infile("ATXTFile.txt");
    while (std::getline(infile, data)) {

        //do some stuff
        //dist are some double values
        allDistances.push_back(dist);
    }

    cout << min_element(allDistances.begin(), allDistances.end()) << endl;

}

Also please define "doesn't work". Compile error? Runtime error? Incorrect result? — Borgleader, Jul 20 '17 at 13:57
since ther's not an example I 'll try to guess. are you doing something like `auto it = min_element` and then printing the actual minimum element using `*it`? `min_element` return an iterator and not the minimum itself. — Davide Spataro, Jul 20 '17 at 13:57
What doesn't work? Show us what you do, what happens and what you expect to happen. — Simon Kraemer, Jul 20 '17 at 13:57
Okay, I edited my question, tell me if it's fine for a clarification — Viktoria, Jul 20 '17 at 14:02
_"it doesn't work, I don't get any output"_ I would expect you to get a compile error. What really happened? — underscore_d, Jul 20 '17 at 14:05

score 8 · Accepted Answer · edited Jun 20 '20 at 09:12

8

The problem is in the way you print the minimum

The following will work: cout << *min_element(allDistances.begin(), allDistances.end()) << endl;

Why?

Because min_element returns an iterator to the minimum not the minimum itself. If you need the actual value, you had to dereference the iterator returned by min_element.

You can see it from the documentation that the signature of min_element is:

template< class ForwardIt > 
ForwardIt min_element( ForwardIt first, ForwardIt last );

and that it returns a ForwardIt i.e. a forward iterator

edited Jun 20 '20 at 09:12

Community

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answered Jul 20 '17 at 14:02

Davide Spataro

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This also finally explains why I don't need to write extra an iterator. Great, thank you! – Viktoria Jul 20 '17 at 14:06

std::min_element on list does not return the minimum

1 Answers1

Why?