Error with a predicate in std::remove_if - c++

Question

I basically have an std::deque of objects, and I want to remove some of these objets according a condition on a given member variable of the objects, so that I use a predicate, but I have errors that I don't really understand.
I am using g++ with the -std=c++11 for STL reasons (shared pointers) but I was trying to work this out on windows with MVS with non c++11 code, so that I am looking for a non c++11 solution, without lamdas etc
The code is :
#include <iostream> // for std::cout and std::endl
#include <cstdio> // for getchar()
#include <memory> // for std::shared_ptr
#include <deque> // for std::deque
#include <algorithm> // for std::earse and std::remove_if
class A
{
private:
int _i;
double _d;
public:
A(int i, double d)
{
_i = i;
_d = d;
}
int geti()const
{
return _i;
}
double getValueOnWhichToCheck()const
{
return _d;
}
};
typedef std::shared_ptr<A> A_shared_ptr;
typedef std::deque<A_shared_ptr> list_type;
void PrintDeque(list_type & dq)
{
if (0 == dq.size())
{
std::cout << "Empty deque." << std::endl;
}
else
{
for (int i = 0 ; i < dq.size() ; ++i)
{
std::cout << i+1 << "\t" << dq[i] << std::endl;
}
}
}
class B
{
public:
double getThreshold() // Non constant for a reason as in real code it isn't
{
return 24.987; // comes from a calculation not needed here so I return a constant.
}
bool Predicate(A_shared_ptr & a)
{
return a->getValueOnWhichToCheck() >= getThreshold();
}
void DoStuff()
{
A_shared_ptr pT1 = std::make_shared<A>(A(2, -6.899987));
A_shared_ptr pT2 = std::make_shared<A>(A(876, 889.878762));
A_shared_ptr pT3 = std::make_shared<A>(A(-24, 48.98924));
A_shared_ptr pT4 = std::make_shared<A>(A(78, -6654.98980));
A_shared_ptr pT5 = std::make_shared<A>(A(6752, 3.141594209));
list_type dq = {pT1,pT2,pT3,pT4,pT5};
PrintDeque(dq);
bool (B::*PtrToPredicate)(A_shared_ptr &) = &B::Predicate;
dq.erase(std::remove_if(dq.begin(), dq.end(), PtrToPredicate),dq.end());
PrintDeque(dq);
}
};
int main()
{
B * pB = new B();
pB->DoStuff();
getchar();
}
and the output of g++ -std=c++11 main.cpp -o main is :
In file included from /usr/include/c++/5/bits/stl_algobase.h:71:0,
from /usr/include/c++/5/bits/char_traits.h:39,
from /usr/include/c++/5/ios:40,
from /usr/include/c++/5/ostream:38,
from /usr/include/c++/5/iostream:39,
from main.cpp:1:
/usr/include/c++/5/bits/predefined_ops.h: In instantiation of ‘bool __gnu_cxx::__ops::_Iter_pred<_Predicate>::operator()(_Iterator) [with _Iterator = std::_Deque_iterator<std::shared_ptr<A>, std::shared_ptr<A>&, std::shared_ptr<A>*>; _Predicate = bool (B::*)(std::shared_ptr<A>&)]’:
/usr/include/c++/5/bits/stl_algo.h:866:20: required from ‘_ForwardIterator std::__remove_if(_ForwardIterator, _ForwardIterator, _Predicate) [with _ForwardIterator = std::_Deque_iterator<std::shared_ptr<A>, std::shared_ptr<A>&, std::shared_ptr<A>*>; _Predicate = __gnu_cxx::__ops::_Iter_pred<bool (B::*)(std::shared_ptr<A>&)>]’
/usr/include/c++/5/bits/stl_algo.h:936:30: required from ‘_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = std::_Deque_iterator<std::shared_ptr<A>, std::shared_ptr<A>&, std::shared_ptr<A>*>; _Predicate = bool (B::*)(std::shared_ptr<A>&)]’
main.cpp:67:73: required from here
/usr/include/c++/5/bits/predefined_ops.h:234:30: error: must use ‘.*’ or ‘->*’ to call pointer-to-member function in ‘((__gnu_cxx::__ops::_Iter_pred<bool (B::*)(std::shared_ptr<A>&)>*)this)->__gnu_cxx::__ops::_Iter_pred<bool (B::*)(std::shared_ptr<A>&)>::_M_pred (...)’, e.g. ‘(... ->* ((__gnu_cxx::__ops::_Iter_pred<bool (B::*)(std::shared_ptr<A>&)>*)this)->__gnu_cxx::__ops::_Iter_pred<bool (B::*)(std::shared_ptr<A>&)>::_M_pred) (...)’
{ return bool(_M_pred(*__it)); }
^

Answer 1

Not a fan of function pointers, but using lambda's this seems to compile... https://ideone.com/0StRcw
dq.erase(std::remove_if(dq.begin(), dq.end(), [this](const std::shared_ptr<A>& a) {
return a->getValueOnWhichToCheck() >= getThreshold();
}),dq.end());
Or without lambdas..
auto predicateToUse = std::bind(&B::Predicate, this, std::placeholders::_1);
dq.erase(std::remove_if(dq.begin(), dq.end(), predicateToUse), dq.end());
Update no auto:
dq.erase(std::remove_if(dq.begin(), dq.end(), std::bind(&B::Predicate, this, std::placeholders::_1)), dq.end());

Answer 2

You are not going to be able to use a non static member function pointer with remove_if. remove_if requires a normal function pointer, static member function pointer or a function object. The reason it cannot use a member function pointer is because it needs an instance of the class in order to be able to call the function and you cannot wrap that into the call
You are either need to make Predicate static, create a function object and pass an instance of that, or use a lambda in the call site.