CODEWITHSUNDEEP
c++boostboost-tuples
cateof
cateof

Reputation: 6758

Find position of element in a vector of boost tuples

I am iterating over a vector of boost::tuples in order to find an element. However I would also like to find the exact position of this element in the vector in order to delete it later. This is the code, however the std::distance does not give me correct value. 

int Controller::isValid(int Id, int& pos) {

        pos = 0;

        for( std::vector< boost::tuple<int,std::string, std::string, std::string> >::const_iterator it = games.begin(); it != games.end(); it++) {

                if( boost::get<0>(*it) == Id) {
                        pos = std::distance< std::vector< boost::tuple<int,std::string, std::string, std::string> >::const_iterator >( games.begin(), it ) ;
                        return 0;
                }
        }

For example for a vector with size equals to 5, the std::distance is 8!

Why? Where is the bug in my code?

Upvotes: 0

Views: 526

Answers (1)

Ami Tavory
Ami Tavory

Reputation: 76297

As Quentin wrote in the comments, an std::vector of boost::tuples can be searched for with std::find_if, just like any other type.

However I would also like to find the exact position of this element in the vector in order to delete it later.

Note that std::vector::erase allows you to erase an element by its iterator.

 #include <algorithm>
 #include <iostream>
 #include <vector>
 #include <string>

 #include <boost/tuple/tuple.hpp>

int main() {
    using tup_t =  boost::tuple<int,std::string, std::string, std::string>;
    std::vector<tup_t> games{
        boost::make_tuple(2, "hello", "world", "bye"), 
        boost::make_tuple(1, "foo", "bar", "baz")};
    auto found = std::find_if(
        std::begin(games), std::end(games), [](const tup_t &t){ return boost::get<0>(t) == 1; });
    std::cout << std::distance(std::begin(games), found) << std::endl;

    if(found != std::end(games))
         games.erase(found);
 }

Upvotes: 1

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