Remove elements from two vectors based on values within one vector
I have two integer vectors of equal length. Let's say I want to delete all elements in the first vector that are NAN. Obviously I am using the remove_if algorithm. Let's say this removes the elements that were at indices 1,2,5. Then I want to remove elements from the second vector at those indices.
What's the most canonical C ++ way to do this?
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This can be done with Boost by creating zip_iterator
and then iterating over the iterators tuple
from both containers in parallel.
Pass a pair from zip_iterators
to first std::remove_if
and the predicate will check the elements of the first vector
for NaN
auto result = std::remove_if(boost::make_zip_iterator(boost::make_tuple(v1.begin(), v2.begin())),
boost::make_zip_iterator(boost::make_tuple(v1.end(), v2.end())),
[](boost::tuple<double, int> const& elem) {
return std::isnan(boost::get<0>(elem));
});
Then use vector::erase
to remove unwanted items.
v1.erase(boost::get<0>(result.get_iterator_tuple()), v1.end());
v2.erase(boost::get<1>(result.get_iterator_tuple()), v2.end());
The pattern required to create iterator gap ranges can be further reduced with boost::combine
the Boost.Range version remove_if
.
auto result = boost::remove_if(boost::combine(v1, v2),
[](boost::tuple<double, int> const& elem) {
return std::isnan(boost::get<0>(elem));
});
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