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## adding a queue to a class

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### #1becklighter  Members

Posted 14 August 2011 - 04:18 PM

I'm attempting to add a queue as a private member of my class, but get the error " syntax error : missing ';' before '<' " on the line where it is declared, I would appreciate any insight into why I'm unable to compile.

here is an example of my code:

#include <queue>

class GameBoard{

private:

queue<int> upcomingPieces;

};



Edited by becklighter, 14 August 2011 - 04:24 PM.

### #2NumberXaero  Prime Members

Posted 14 August 2011 - 04:22 PM

I'm attempting to add a queue as a private member of my class, but get the error " syntax error : missing ';' before '<' " on the line where it is declared, I would appreciate any insight into why I'm unable to compile.

here is an example of my code:

#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
}


#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
};  // <---


### #3becklighter  Members

Posted 14 August 2011 - 04:26 PM

I'm attempting to add a queue as a private member of my class, but get the error " syntax error : missing ';' before '<' " on the line where it is declared, I would appreciate any insight into why I'm unable to compile.

here is an example of my code:

#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
}


#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
};  // <---


Thanks for pointing out that my class was missing the ";", but that isn't the problem. The code in my project actually had that part right, I just didn't copy it all over, any other ideas?

### #4Wooh  Members

Posted 14 August 2011 - 04:29 PM

It's called std::queue

### #5DoctorGlow  Members

Posted 14 August 2011 - 06:05 PM

I'm attempting to add a queue as a private member of my class, but get the error " syntax error : missing ';' before '<' " on the line where it is declared, I would appreciate any insight into why I'm unable to compile.

here is an example of my code:

#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
}


#include <queue>

class GameBoard{
private:
queue<int> upcomingPieces;
};  // <---


and

#include <queue>

class GameBoard{
private:
std::queue<int> upcomingPieces; // <-- std::
};


### #6Tournicoti  Prime Members

Posted 15 August 2011 - 01:47 AM

Hello

There are 2 options :
• use std::queue instead of queue everywhere
• or put using namespace std; after the #include<queue> (sorry )

### #7rip-off  Moderators

Posted 15 August 2011 - 01:54 AM

It is advised against putting using directives in header files, as there is no way to "un-use" a namespace.

### #8Tournicoti  Prime Members

Posted 15 August 2011 - 02:19 AM

....as there is no way to "un-use" a namespace.

Why would you 'un-use' a namespace ?
std is used with vector, string,list,etc.... so putting std:: everywhere is not very elegant

### #9ApochPiQ  Moderators

Posted 15 August 2011 - 02:24 AM

....as there is no way to "un-use" a namespace.

Why would you 'un-use' a namespace ?
std is used with vector, string,list,etc.... so putting std:: everywhere is not very elegant

What if I want to call something foo::string? If I #include your header, I now have a name collision between foo::string and std::string.

You should only be "using" namespaces from within .cpp files, preferably after all headers are included, and then only as absolutely necessary.

Wielder of the Sacred Wands

### #10Tournicoti  Prime Members

Posted 15 August 2011 - 02:28 AM

What about inline classes ? Where else could you put the using directive ? Isn't it a bad idea to call a class 'string' anyway ?

### #11Hodgman  Moderators

Posted 15 August 2011 - 02:28 AM

std is used with vector, string,list,etc.... so putting std:: everywhere is not very elegant

A standard C++ rule, that's in almost every C++ style guide I've ever read is: Never use a "using namespace" statement globally in a header.

It pollutes the global namespace in the same way that #defines do, which is something that namespaces were designed to avoid.
e.g. this is the problem with defines:
#include "windows.h"
#include <algorithm>
int a = 2, b = 4;
int c = std::max( a, b );//compile error - windows contains a #define max line!!!

Now, namespaces solve these kinds of problems for us.
Here is some perfectly valid code:
#include <queue>
class queue{};
queue q;//makes my queue, not a std::queue
std::queue<int> q2;//makes a std::queue
Now, if we include a header that has rudely used "using namespace" inside it:
#include "Adaline.h" // includes "using namespace std;"
#include <queue>
class queue{};
queue q; // compile error? This code was fine a minute ago?!! thanks Adaline ;)
std::queue<int> q2;

If you really do want to use "using namespace" in a header, then you must at least always wrap it in your own namespace, e.g.
//Adaline.h
#include <queue>
{
using namespace std;//ok, you've only polluted your own namespace
}

Isn't it a bad idea to call a class 'string' anyway ?

The concept extends beyond the std namespace.
Maybe I'm using two different bits of C++ middleware that both define a Vector3 type? If I using-namespace'd them, I'd get conflicts between the two libraries.

### #12Tournicoti  Prime Members

Posted 15 August 2011 - 02:33 AM

std is used with vector, string,list,etc.... so putting std:: everywhere is not very elegant

A standard C++ rule, that's in almost every C++ style guide I've ever read is: Never use a "using namespace" statement globally in a header.

It pollutes the global namespace in the same way that #defines do, which is something that namespaces were designed to avoid.
e.g. this is the problem with defines:
#include "windows.h"
#include <algorithm>
int a = 2, b = 4;
int c = std::max( a, b );//compile error - windows contains a #define max line!!!

Now, namespaces solve these kinds of problems for us.
Here is some perfectly valid code:
#include <queue>
class queue{};
queue q;//makes my queue, not a std::queue
std::queue<int> q2;//makes a std::queue
Now, if we include a header that has rudely used "using namespace" inside it:
#include "Adaline.h" // includes "using namespace std;"
#include <queue>
class queue{};
queue q; // compile error? This code was fine a minute ago?!! thanks Adaline!
std::queue<int> q2;

If you really do want to use "using namespace" in a header, then you must at least always wrap it in your own namespace, e.g.
//Adaline.h
#include <queue>
{
using namespace std;//ok, you've only polluted your own namespace
};

Thanks for you're explanation (I mean it)
No need to be rude anyway

### #13Hodgman  Moderators

Posted 15 August 2011 - 02:35 AM

No need to be rude anyway

Sorry if I came across as rude! Just trying to get to the point

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