Why is g++ not able to compile tuples?

Question

#include <iostream>
#include <tuple>
#include <string>
using namespace std;

int main(){
  tuple<string, string, string> x;
  x = make_tuple("hi", "a", "b");
  cout << get<0>(x) << endl << endl;

}

I've been having difficulties with my program, so I wrote a simpler one and even this does not work. I do not understand why there is a problem after reviewing the documentation several times. It also compiles fine on XCode but for some reason breaks down on g++.

Here is the full error message:

test.cpp:6:3: error: use of undeclared identifier 'tuple'

tuple x;

^

test.cpp:6:9: error: unexpected type name 'string': expected expression

tuple x;
    ^
test.cpp:7:3: error: use of undeclared identifier 'x'

x = make_tuple("hi", "a", "b");

^

test.cpp:7:7: error: use of undeclared identifier 'make_tuple'

x = make_tuple("hi", "a", "b");
  ^
test.cpp:8:11: error: reference to overloaded function could not be resolved; did you mean to call it? cout << get<0>x << endl << endl;

The command I am using is g++ test.cpp

It looks like all you need is `get<0>(x)` instead of `get<0>x`. — Emmanuel Mathi-Amorim, Dec 11 '16 at 20:50
A duplicate of http://stackoverflow.com/q/6209067/2564301, but the OP did not look further into this after finding a solution that worked around it. — Jongware, Dec 11 '16 at 20:50
[Cannot reproduce](http://melpon.org/wandbox/permlink/wOTQuJ2dLXcBg5Kk) after fixing the missing `#include ` and the missing parans in `get<0>(x)`. Looks like you need to upgrade your compiler. — Baum mit Augen, Dec 11 '16 at 20:50
You should have included `` then, because now we're all looking at that as the cause. — Jongware, Dec 11 '16 at 20:51
No, `` is not required to include ``. It is allowed to, but not required to. — Pete Becker, Dec 11 '16 at 20:53
[Do I have to include string beside iostream ..](http://stackoverflow.com/questions/16506095/do-i-have-to-use-include-string-beside-iostream) — Jongware, Dec 11 '16 at 20:54
Thanks, It was the -std=c++11 that did the trick. Didn't know it was necessary — JobHunter69, Dec 11 '16 at 20:54

score 6 · Accepted Answer · answered Dec 11 '16 at 20:49

6

Try #include <string>.

Possibly (depending on your version og gcc) you also need -std=c++11 on the command line.

answered Dec 11 '16 at 20:49

jbab

469
4
9

score 1 · Answer 2 · answered Dec 11 '16 at 20:51

The tuple is fine; what you're trying to make it a tuple of is not.

You did not #include <string>!

Thus the word "string" means nothing to your compiler, and it has no idea what you want it to do. It can't even tell that you meant it to be a type, so it can't tell that by the word "tuple" you meant "std::tuple". So on, and so forth…

Why is g++ not able to compile tuples?

2 Answers2