RE: STL iterator problem

RE: STL iterator problem

[Martin York]

Here is what I have found.
Hope this helps.

> for(B::iterator i = the_Container->Begin(); i != the_Container->end();
++i  )

The problem is cause because B is a template class and g++ can not
guarantee that B::iterator is a type (could be a static member variable)
when it fist parses the function. g++ adheres strictly to the standard
which requires that in these situations you use the typename keyword to
disambigiufy the situation. Sorry can not quote chapter and verse on
what part of the standard.

PS. Also note that the method Begin() should probably be begin().

> for(typename B::iterator i = the_Container->begin(); i !=
the_Container->end(); ++i  )


Martin


-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
Behalf Of Yogesh Kini
Sent: 24 November 2004 03:21
To: gcc-help@gcc.gnu.org
Subject: STL iterator problem

Hi,
Please take a look at the code snippet below.
The code compiles fine with Microsoft VC++ but gives a error with gcc(as
indicated below) I am trying to port the file from msvc to gcc. Can
anyone suggest me a work around. 

Thanks
Yogesh


#include <stdio.h>
#include <list>
 
template <class B>
class parent
{
public:
	B * m_Container;			
	void funone();
	void CreateList()
	{
		m_Container = new B();  
		m_Container->push_front(1);		
		m_Container->push_front(2);		
		m_Container->push_front(3);		
		m_Container->push_front(4);		
	}
	B * GetList()
	{
		return (m_Container);
	}
};
 

template<class B>
void parent<B>::funone()
{
	B * the_Container = GetList();
	for(B::iterator i = the_Container->Begin(); i !=
the_Container->end(); ++i  )  -> Error Here: Parse error before "="
token
	{
		printf("%d ",*i);	
	}	
}
 
int main()
{ 
	parent<std::list<int>> the_instance;
	the_instance.CreateList();
	the_instance.funone();
}

Error: parse error before "=" token



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Re: STL iterator problem

[Eljay Love-Jensen]

Hi jlh,

 >But still I don't get why this is wrong.  Is only because the compiler 
can't tell whether it's a typename or something else at parse time?

Correct, compilers are not allowed to ASSUME (as per ISO 14882) that it is 
a typename.

Compilers that do make that ASSUMPTION are in violation of ISO 
14882.  (Which is why it is wrong.)

GCC works hard to be compliant.  EDG is often lauded as a very, very 
compliant compiler (even implementing the dusty-hard-to-reach ISO 14882 
items).  MSVC comes up short in this regard.  I'm out of experience with 
Metrowerks or Borland these days, but I have fond memories of them.

HTH,
--Eljay

Re: STL iterator problem

[jlh]

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> gcc is right to reject this code, something more
> standard compliant should pass :
> 
> for(typename B::iterator i; ...)

Yep, conveniently, gcc-3.4.3 even suggests it:

a.cpp:29: error: dependent-name ` B::iterator' is parsed as a non-type,
           but instantiation yields a type
a.cpp:29: note: say `typename  B::iterator' if a type is meant

But still I don't get why this is wrong.  Is only because the compiler
can't tell whether it's a typename or something else at parse time?

btw, take care with "parent<std::list<int>>".  Apparently GCC now
gets it right, but to be portable, better write "parent<std::list<int> >",
to avoid parsing a shift operator instead.

Cheers,
jlh

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Re: STL iterator problem

[Philippe Haution]

Hello,

gcc is right to reject this code, something more
standard compliant should pass :

for(typename B::iterator i; ...)

Regards,

PH
 --- Yogesh Kini <kini1982@postmaster.co.uk> a écrit :

> Hi,
> Please take a look at the code snippet below.
> The code compiles fine with Microsoft VC++ but gives
> a error with gcc(as indicated below)
> I am trying to port the file from msvc to gcc. Can
> anyone suggest me a work around. 
> 
> Thanks
> Yogesh
> 
> 
> #include <stdio.h>
> #include <list>
>  
> template <class B>
> class parent
> {
> public:
> 	B * m_Container;			
> 	void funone();
> 	void CreateList()
> 	{
> 		m_Container = new B();  
> 		m_Container->push_front(1);		
> 		m_Container->push_front(2);		
> 		m_Container->push_front(3);		
> 		m_Container->push_front(4);		
> 	}
> 	B * GetList()
> 	{
> 		return (m_Container);
> 	}
> };
>  
> 
> template<class B>
> void parent<B>::funone()
> {
> 	B * the_Container = GetList();
> 	for(B::iterator i = the_Container->Begin(); i !=
> the_Container->end(); ++i  )  -> Error Here: Parse
> error before "=" token
> 	{
> 		printf("%d ",*i);	
> 	}	
> }
>  
> int main()
> { 
> 	parent<std::list<int>> the_instance;
> 	the_instance.CreateList();
> 	the_instance.funone();
> }
> 
> Error: parse error before "=" token
> 
> 
> 
> ___________________________________________________
> Have your own email and web address for life.
> 
> http://www.homemaster.net - Homemaster. Come
> Together. Online.
> 
>  


	

	
		
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STL iterator problem

[Yogesh Kini]

Hi,
Please take a look at the code snippet below.
The code compiles fine with Microsoft VC++ but gives a error with gcc(as indicated below)
I am trying to port the file from msvc to gcc. Can anyone suggest me a work around. 

Thanks
Yogesh


#include <stdio.h>
#include <list>
 
template <class B>
class parent
{
public:
	B * m_Container;			
	void funone();
	void CreateList()
	{
		m_Container = new B();  
		m_Container->push_front(1);		
		m_Container->push_front(2);		
		m_Container->push_front(3);		
		m_Container->push_front(4);		
	}
	B * GetList()
	{
		return (m_Container);
	}
};
 

template<class B>
void parent<B>::funone()
{
	B * the_Container = GetList();
	for(B::iterator i = the_Container->Begin(); i != the_Container->end(); ++i  )  -> Error Here: Parse error before "=" token
	{
		printf("%d ",*i);	
	}	
}
 
int main()
{ 
	parent<std::list<int>> the_instance;
	the_instance.CreateList();
	the_instance.funone();
}

Error: parse error before "=" token



___________________________________________________
Have your own email and web address for life.

http://www.homemaster.net - Homemaster. Come Together. Online.