Why is this swap function call ambiguous?

Question

I wanted to swap two number using a template but why does this swap(x, y); give an error as an ambiguous call.

#include <iostream>
using namespace std;

template <class T>

void swap(T &a, T &b) {
    T temp = a;
    a = b;
    b = temp;
}

int main () {
    int x = 14;
    int y = 7;
    swap(x, y);
    cout << x << y;
}

@LoganMurphy: That is not what "class" means in template land... not even close. Any type will do. — Ed S., Dec 12 '13 at 21:06
Because you did `using namespace std;` and `` has been known to include `` (or `` in C++11), but to my knowledge, not much anymore with newer versions of implementations. — chris, Dec 12 '13 at 21:06
By any chance is this not your actual code and, if so, does your actual code include `` and a `using namespace std;` or another file which defines `swap` (or includes ``)? — Ed S., Dec 12 '13 at 21:07
Your edit shows `using namespace std;` now. That would be your problem. — Ed S., Dec 12 '13 at 21:08
Thanks a lot guys i changed the swap to swaap and it worked fine! — Chiran, Dec 12 '13 at 21:12
@Chiran, Better yet, don't do `using namespace std;` and put it in your own namespace, even if it's an anonymous one. — chris, Dec 12 '13 at 21:14
Lots of good discussion here: http://stackoverflow.com/q/1452721/10077 — Fred Larson, Dec 12 '13 at 21:20
...changing your function name to `swaap` is probably the worst way to fix this — Ed S., Dec 12 '13 at 21:21

Ed S. · Accepted Answer · 2013-12-12T21:22:35.483

6

#include <iostream>
using namespace std;

iostream must be including algorithm and, since you decided to include the entire std namespace in your file, you have a collision with std::swap. Remove using namespace std;

EDIT: As @chris points out in the comments, std::swap was moved to <utility> in C++11.

edited Dec 12 '13 at 21:22

answered Dec 12 '13 at 21:09

Ed S.

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And if it's C++11, one of those must be including ``. – chris Dec 12 '13 at 21:11
@chris: Ah yeah, good point – Ed S. Dec 12 '13 at 21:20

Why is this swap function call ambiguous?

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