Some problems with std::vector and nested templates

J

jubelbrus

Hi

I'm trying to do the following.

#include <vector>
#include <boost/thread/mutex.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>

class {
boost::mutex m_lock;
std::vector<boost::tuple<uint32_t, boost::shared_ptr<T> > >
m_vector;

template <class T> boost::shared_ptr<T> list::<T>getitem(uint32_t id)
{
boost::mutex::scoped_lock lock(m_lock);

std::vector said:
::iterator pos =
Click to expand...
find_if(m_vector.begin(), m_vector.end(), compare_list<T>(id),
m_vector.begin());

if (pos != m_vector.end())
return *pos;

return boost::shared_ptr(NULL);
};

but I get the following error
error: expected ';' before 'pos'

I don't understand why I'm getting this error because the definition
of std::vector works, it's just the iterator statement that doesn't.
 
R

Robert Bauck Hamar

jubelbrus said:
Hi

I'm trying to do the following.

#include <vector>
#include <boost/thread/mutex.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>

class {
boost::mutex m_lock;
std::vector<boost::tuple<uint32_t, boost::shared_ptr<T> > >
m_vector;
Click to expand...

I'm assuming uint32_t might be typedefed somewhere.
What's T? This is not a template?
template <class T> boost::shared_ptr<T> list::<T>getitem(uint32_t id)
Click to expand...

huh?
template <class T>
boost::shared_ptr<T>
list<T>::getitem(uint32_t id)
?
What's list?
{
boost::mutex::scoped_lock lock(m_lock);


find_if(m_vector.begin(), m_vector.end(), compare_list<T>(id),
m_vector.begin());
Click to expand...

typename std::vector said:
::iterator pos = find_if(...)
Click to expand...

You need typename here said:
if (pos != m_vector.end())
return *pos;
Click to expand...

*pos is a tuple, not a shared_ptr
 
J

jubelbrus

Sorry about the misspellings...

This is what I'm trying to do:
Write a template class that stores a list of boost::shared_ptr<T> with
a index and is thread safe, where T would be that template <class T>
stuff..

I got the getitem function compiling by using typename, tanks.. but
I've discovered some compile problems with my insert code.

#include <stdint.h>
#include <vector>
#include <boost/thread/mutex.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>

template <class T>
class list{
boost::mutex m_lock;
std::vector<boost::tuple<uint32_t, boost::shared_ptr<T> > >
m_vector;

uint32_t m_nextid;

uint32_t insert(boost::shared_ptr<T>);
}

template <class T>
uint32_t list<T>::insert(boost::shared_ptr<T>)
{
typename boost::tuples::tuple<uint32_t, boost::shared_ptr<T> >
add_item(m_nextid, item);
typename std::vector said:
m_vector;
Click to expand...

boost::mutex::scoped_lock lock(m_lock);

m_vector.insert( add_item );
return m_nextid++;

};

I get the following error:
list.h: In member function 'uint32_t
stdtools::list<T>::insert(boost::shared_ptr<T>) [with T = int]':
tester_a.cpp:10: instantiated from here
list.h:90: error: no matching function for call to
'std::vector<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>,
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >
::insert(boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
Click to expand...
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>&)'
/usr/include/c++/4.0.0/bits/vector.tcc:93: note: candidates are:
typename std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(__gnu_cxx::__normal_iterator<typename _Alloc::pointer,
std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp =
boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>, _Alloc =
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >]
/usr/include/c++/4.0.0/bits/stl_vector.h:657: note:
void std::vector<_Tp,
_Alloc>::insert(__gnu_cxx::__normal_iterator<typename _Alloc::pointer,
std::vector<_Tp, _Alloc> >, size_t, const _Tp&) [with _Tp =
boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>, _Alloc =
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >]

Anybody??
 
J

John Harrison

jubelbrus said:
Sorry about the misspellings...

This is what I'm trying to do:
Write a template class that stores a list of boost::shared_ptr<T> with
a index and is thread safe, where T would be that template <class T>
stuff..

I got the getitem function compiling by using typename, tanks.. but
I've discovered some compile problems with my insert code.

#include <stdint.h>
#include <vector>
#include <boost/thread/mutex.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>

template <class T>
class list{
boost::mutex m_lock;
std::vector<boost::tuple<uint32_t, boost::shared_ptr<T> > >
m_vector;

uint32_t m_nextid;

uint32_t insert(boost::shared_ptr<T>);
}

template <class T>
uint32_t list<T>::insert(boost::shared_ptr<T>)
{
typename boost::tuples::tuple<uint32_t, boost::shared_ptr<T> >
add_item(m_nextid, item);


boost::mutex::scoped_lock lock(m_lock);

m_vector.insert( add_item );
Click to expand...

Perhaps you mean

m_vector.push_back( add_item );

There is no method of vector called insert that takes a single argument.

john
 
R

Robert Bauck Hamar

jubelbrus said:
Sorry about the misspellings...

This is what I'm trying to do:
Write a template class that stores a list of boost::shared_ptr<T> with
a index and is thread safe, where T would be that template <class T>
stuff..

I got the getitem function compiling by using typename, tanks.. but
I've discovered some compile problems with my insert code.

#include <stdint.h>
#include <vector>
#include <boost/thread/mutex.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>

template <class T>
class list{
boost::mutex m_lock;
std::vector<boost::tuple<uint32_t, boost::shared_ptr<T> > >
m_vector;

uint32_t m_nextid;

uint32_t insert(boost::shared_ptr<T>);
}

template <class T>
uint32_t list<T>::insert(boost::shared_ptr<T>)
{
typename boost::tuples::tuple<uint32_t, boost::shared_ptr<T> >
add_item(m_nextid, item);
Click to expand...

There should be no typename here.

nor here.

typename are needed in:
T::something
or
someclass<T>::something
To put it very short.

This is because the compiler cannot possibly know what something is. The
first is obvious. The second:

template <class T>
class someclass {
public:
typedef T something;
};

int p;

template <class T>
void foo() {
someclass<T>::something * p; /*Missing typename and definition of local p
or multiplication? Standard says multiplication */
}

template <>
class someclass<int> {
public:
int something;
};

int someclass<int>::something = 3;

int main() {
p = 42;
boost::mutex::scoped_lock lock(m_lock);

m_vector.insert( add_item );
return m_nextid++;

};

I get the following error:
list.h: In member function 'uint32_t
stdtools::list<T>::insert(boost::shared_ptr<T>) [with T = int]':
tester_a.cpp:10: instantiated from here
list.h:90: error: no matching function for call to
Click to expand...

// beginning
'std::vector<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>,
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>&)'
Click to expand...

//end

Shorter:
std::vector said:
/usr/include/c++/4.0.0/bits/vector.tcc:93: note: candidates are:
//beginning

typename std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(__gnu_cxx::__normal_iterator<typename _Alloc::pointer,
std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp =
boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>, _Alloc =
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >]
Click to expand...

//end
shorter:
std::vector said:
/usr/include/c++/4.0.0/bits/stl_vector.h:657: note:
void std::vector<_Tp,
//beginning

_Alloc>::insert(__gnu_cxx::__normal_iterator<typename _Alloc::pointer,
std::vector<_Tp, _Alloc> >, size_t, const _Tp&) [with _Tp =
boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>, _Alloc =
std::allocator<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type> >]
Click to expand...

//end

shorter:
std::vector<...>::insert(std::vector<...>::iterator, size_t, const
tuple<...>&)

Read the messages. They're long and hairy, but it's possible. Matching
parens is a good start.
 
J

John Harrison

Perhaps you mean
oh... :)

thanks
Click to expand...

Those super long error messages make you think there must be something
really significant wrong with your code. But sometimes it's just the
obvious stuff.

john
 
R

Roland Pibinger

I get the following error:
list.h: In member function 'uint32_t
stdtools::list<T>::insert(boost::shared_ptr<T>) [with T = int]':
tester_a.cpp:10: instantiated from here
list.h:90: error: no matching function for call to
'std::vector<boost::tuples::tuple<uint32_t, boost::shared_ptr<int>,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type,
boost::tuples::null_type, boost::tuples::null_type>,
Click to expand...
[snipped template jumble]

Why don't you ask Boost when you've got a Boost problem?
http://www.boost.org/more/mailing_lists.htm#users
 
R

Roland Pibinger

Those super long error messages make you think there must be something
really significant wrong with your code. But sometimes it's just the
obvious stuff.
Click to expand...

Obviously, there is 'something really significant wrong' with Boost.
 
J

Jerry Coffin

Obviously, there is 'something really significant wrong' with Boost.
Click to expand...

Hardly -- you can get the same sort of problems without using Boost. The
problem is sufficiently widespread that Leor Zolman has put quite a bit
of work into stlfilt, to try to make error messages more readable. As I
understand it, lousy error messages from templated code also provided
the motivation for the work that led to Concepts.
 
J

John Harrison

Roland said:
Obviously, there is 'something really significant wrong' with Boost.
Click to expand...

At least one compiler I know would quote typedefs that you use back to
you in error messages. So if the OP had written

typedef typename boost::tuple<uint32_t, boost::shared_ptr<T> > item_type;

he might have got a considerably shorter error message.

john
 
R

Roland Pibinger

Hardly -- you can get the same sort of problems without using Boost.
Click to expand...

Hardly. No one abuses templates the way Boost does.
The
problem is sufficiently widespread that Leor Zolman has put quite a bit
of work into stlfilt, to try to make error messages more readable.
Click to expand...

The treatment of symptoms is not a cure.
As I
understand it, lousy error messages from templated code also provided
the motivation for the work that led to Concepts.
Click to expand...

You mean Stroustrup's where-clause? OMG, please no!
 
J

Jerry Coffin

Hardly. No one abuses templates the way Boost does.
Click to expand...

Actually, everybody else who wants to accomplish the same sorts of
things tends to write fairly similar code -- there are only so many ways
to skin a cat...
The treatment of symptoms is not a cure.
Click to expand...

I didn't say it was a cure -- but note the "stl" in its name -- it's for
fixing messages that arise from the standard library, NOT Boost.
You mean Stroustrup's where-clause? OMG, please no!
Click to expand...

I mean Concepts. For the formal paper see:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2193.pdf

If you care, you can find quite a bit more at:

http://conceptgcc.wordpress.com/

There will probably be at least a few more minor changes by the time the
standard is finalized, but most of it seems nearly certain to be in C++
0x.
 

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