12 replies to this topic

[becklighter]

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.

[NumberXaero]

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;
};  // <--- 

[becklighter]

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?

[Wooh]

It's called std::queue

[DoctorGlow]

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::
}; 

[Tournicoti]

Hello

There are 2 options :

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

[rip-off]

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

[Tournicoti]

....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

[ApochPiQ]

....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

"using" a namespace in a header is bad.

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.

[Tournicoti]

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

[Hodgman]

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>
namespace adaline
{
    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.

[Tournicoti]

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>
namespace adaline
{
    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

[Hodgman]

No need to be rude anyway

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