Re: A predicate testing a data member
On 11 ago, 15:42, Seungbeom Kim <musip...@bawi.org> wrote:
Given the struct below:
struct T
{
bool f() const;
};
I can use std::mem_fun(&T::f) as a predicate testing f() on each T object,
as in:
std::vector<T*> tv(...);
n = std::count_if(tv.begin(), tv.end(), std::mem_fun(&T::f));
Can I do the same thing with a data member, instead of a member function,
for a struct such as the one below:
struct T
{
bool d;
};
std::vector<T*> tv(...);
n = std::count_if(tv.begin(), tv.end(), /* ? ? ? */);
... without writing a custom functor, of course. :)
I guess you want something like a "mem_data" instead of mem_func
template<class T, class T2>
struct data_from
{
T2 T::* m_p;
data_from( T2 T::* p) : m_p(p) { }
T2 operator ()(const T *p) const { return p->*m_p; }
};
template<class T, class T2>
data_from<T, T2> mem_data(T2 T::* p)
{
return data_from<T, T2>(p);
}
n = std::count_if(vec.begin(), vec.end(), men_data(&T::d));
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