FilterIterator.hpp

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#ifndef FOCS_FILTERITERATOR
#define FOCS_FILTERITERATOR
 
#include <iterator>
#include <string>
#include <unordered_map>
#include <vector>
 
namespace focs {
template <class InputIterator, class UnaryPredicate>
class FilterIterator {
public:
    FilterIterator(InputIterator first, InputIterator last, UnaryPredicate pred) : first_{first}, it_{first}, last_{last}, pred_{pred} {
        while (it_ != last_) {
            if (pred_(*it_)) {
                break;
            }
            it_++;
        }
    }
 
    bool operator!=(const FilterIterator& it) {
        return it.it_ != this->it_;
    }
 
    bool operator==(const FilterIterator& it) {
        return it.it_ == this->it_;
    }
 
    InputIterator operator*() {
        return it_;
    }
 
    FilterIterator operator++() {
        while (it_ != last_) {
            it_++;
            if (it_ == last_ || pred_(*it_)) {
                return *this;
            }
        }
        return end();
    }
 
    FilterIterator begin() const {return FilterIterator(first_, last_, pred_);}
    FilterIterator end() const {return FilterIterator(last_, last_, pred_);}
private:
    const InputIterator first_; 
    InputIterator it_; 
    const InputIterator last_; 
    const UnaryPredicate pred_; 
};
} // namespace focs
 
#endif // FOCS_FILTERITERATOR