On Mar 7, 4:56 pm, "joseph cook" <joec...@gmail.comwrote:
I am getting a compile error on any compiler I try, so I know I have
an error here. Can anyone see it?
//includes
class Foo
{
public:
Foo(int a){m_hi = a;}
int hi(){return m_hi;}
int m_hi;
};
int main()
{
std::vector<Foo *data;
data.push_back(new Foo(3));
max_element(data.begin(),
data.end(),
std::mem_fun(&Foo::hi));
}
gives a compile error:
in gcc: stl_algo.h:4565: error: no match for call to
'(std::mem_fun_t<int, Foo>) (Foo*&,Foo*&)'
stl_function.h:600: note: candidates are: _Ret
std::mem_fun_t<_Ret,_Tp>::operator()(_Tp*) const [with _Ret = int,
_Tp = Foo]
help!
}
You're specifying a member function adapter where you need a
comparator. A member function is invoked like:
some_mem_fun( *i )
where some_mem_fun is the functor resulting from your mem_fun call and
i is an iterator in the range [begin, end). Note that the functor only
takes one parameter. A comparator, on the other hand, has a signature
like:
bool less_than( a, b )
Probably what you intended is something like this:
for_each( data.begin(),
data.end(),
mem_fun(&Foo::hi));
or
int mx = numeric_limits<int>::min();
for( vector<Foo*>::const_iterator i=data.begin();
i != data.end(); ++i )
{
mx = max( (*i)->hi(), mx );
}
(Of course, this would require Foo::hi() to be a const function.)
Cheers! --M
