Hello everyone
Imagine a class "numbers" that contains some values and methods like
getEvenValues(), getOddValues(), getValuesLarger100() etc. Those methods
return an iterator range of filter_iterators. In the the code I posted
below, I'd have to define a different iterator_range of filter_iterator
types for all the different methods (numbers::EvenFilterRange,
numbers::OddFilterRange etc.). Is there some way to "hide" the type of
the predicate used in a filter_iterator, so that it would be possible to
have a generic "NumberRange" type for the return values of all methods?
Something like:
class numbers {
typedef NumberRange ????;
NumberRange getEvenValues() const;
NumberRange getOddValues() const;
NumberRange getValuesLarger100() const;
}
Thanks for your hints
James
/*********************************************/
#include <vector>
#include <iostream>
#include
#include
#include
using namespace std;
using namespace boost;
/*********************************************/
template<typename T>
struct is_even {
bool operator()(const T &t) {
return t % 2 == 0;
}
};
template<typename T>
struct is_odd {
bool operator()(const T &t) {
return t % 2 != 0;
}
};
/*********************************************/
class numbers {
public:
typedef vector<int> NumberContainer;
typedef NumberContainer::const_iterator NumberIter;
typedef iterator_range<
filter_iterator<
is_evennumbers::NumberContainer::value_type,
NumberIter>
> EvenFilterRange;
numbers() {
copy(
counting_iteratorNumberContainer::value_type(0),
counting_iteratorNumberContainer::value_type(100),
back_inserter(m_vec)
);
}
template<typename Pred>
iterator_range > getValues(const
Pred &pred) {
return make_iterator_range(
make_filter_iterator(pred, m_vec.begin(), m_vec.end()),
make_filter_iterator(pred, m_vec.end(), m_vec.end())
);
}
EvenFilterRange getEvenValues() {
typedef is_evennumbers::NumberContainer::value_type PredType;
PredType is_even_predicate;
return getValues(is_even_predicate);
};
private:
NumberContainer m_vec;
};
/*********************************************/
template<typename T>
struct print_number {
void operator()(const T &t) {
cout << "Number: " << t << endl;
}
};
/*********************************************/
int main()
{
numbers n;
numbers::EvenFilterRange even_filter_range = n.getEvenValues();
print_numbernumbers::NumberContainer::value_type printer;
for_each(begin(even_filter_range), end(even_filter_range), printer);
}
