I want to write a function like print_all
described below.
#include <iterator>
#include <vector>
template <typename V>
void print_all(std::iterator<std::input_iterator_tag, V> it) {
for (; it != std::end(it); ++it) {
V item = *it;
// do stuff with item
}
}
int main() {
std::vector<int> myvec (10);
print_all(myvec.cbegin());
return 0;
}
How do I declare print_all
such that it can accept any iterator over type V
?
I want to do this in a typesafe way. A better example of a use case would be an accumulator
#include <iterator>
#include <vector>
#include <functional>
template <typename V, typename K>
K accumulate(
std::function<K(K, V)> accumulator,
std::iterator<std::input_iterator_tag, V> it,
std::iterator<std::input_iterator_tag, V> end,
K initial) {
K sum = initial;
for (; it != end; ++it) {
V item = *it;
sum = accumulator(sum, item);
}
return sum;
}
Now you see why this question is not a duplicate of this . I feel like there would be a typesafe way to do this where the compiler makes sure the iterator iterates over the correct type. That is why I hesitate to accept Steve Lorimer's answer.
Assuming you have the required overloaded std::ostream
operators , you can just make the actual iterator your function template's type
template<typename IterT>
void print_all(IterT begin, IterT end)
{
while (begin != end)
std::cout << *begin++ << ", ";
std::cout << '\n';
}
As stated, this will only work if you have the requisite std::ostream& operator<<(...)
overload.
You would call it as follows:
int main()
{
std::vector<int> myvec;
// populate myvec...
print_all(std::begin(myvec), std::end(myvec));
return 0;
}
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