CODEWITHSUNDEEP
c++hashmapiterator
Rikib1999
Rikib1999

Reputation: 209

C++ map iterator over values

I have this code:

template <typename Iter>
class map_iterator : public std::iterator<std::bidirectional_iterator_tag, typename Iter::value_type::second_type> {
public:
    map_iterator() {}
    map_iterator(Iter j) : i(j) {}
    map_iterator& operator++() { ++i; return *this; }
    map_iterator operator++(int) { auto tmp = *this; ++(*this); return tmp; }
    map_iterator& operator--() { --i; return *this; }
    map_iterator operator--(int) { auto tmp = *this; --(*this); return tmp; }
    bool operator==(map_iterator j) const { return i == j.i; }
    bool operator!=(map_iterator j) const { return !(*this == j); }
    reference operator*() { return i->second; }
    pointer operator->() { return &i->second; }
protected:
    Iter i;
};

template <typename Iter>
inline map_iterator<Iter> make_map_iterator(Iter j) { return map_iterator<Iter>(j); }

using route_departure_container = std::map<packed_time, route_departure_o>;

template <typename Iter>
using route_departure_const_iterator = map_iterator;

route_departure_const_iterator departure_at(const std::pair<key, const platform_route_o&>& pr, packed_time tm);

I have map using route_departure_container = std::map<packed_time, route_departure_o>; and I want to iterate through this map in a way that the iterator would reference only on the value and not the pair<key, value>.

The problem I have is in the last line route_departure_const_iterator departure_at(const std::pair<key, const platform_route_o&>& pr, packed_time tm); where route_departure_const_iterator is underlined with red and it says: argument list for alias template "route_departure_const_iterator" is missing. I tried to insert template <typename Iter> above this line but it did not help. What should I do?

Upvotes: 0

Views: 65

Answers (1)

Blindy
Blindy

Reputation: 67380

The same way you wrote the above declaration:

template <typename Iter>
inline map_iterator<Iter> make_map_iterator(Iter j) { return map_iterator<Iter>(j); }

You also need to write your problematic declaration:

template <typename Iter>
route_departure_const_iterator<Iter> departure_at(const std::pair<key, const platform_route_o&>& pr, packed_time tm);

Because the way you defined route_departure_const_iterator is just a plain, non-const alias to map_iterator, so you use it the same.

Upvotes: 1

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