CODEWITHSUNDEEP
c++vectorc++98
Roman Rdgz
Roman Rdgz

Reputation: 13254

std::remove_if usage in C++98

I was looking for a smart way of erasing some elements in a vector while iterating, and found this question.

Of course, it won't work for me, since C++98 doesn't have lambdas. Looked for remove_if info and found this at cppreference. So this is how my code looks:

#include <algorithm>
#include <vector>

bool isOutageValid(const Outage& outage){
    return outage.getEndTime() >= 0;
}

std::vector<Outage> outages;
// Some stuff to fill the vector

outages.erase(std::remove_if(outages.begin(), outages.end(), isOutageValid));

for(vector<Outage>::iterator o=outages.begin(); o!=outages.end(); o++){
    std::cout << o->getStartTime() << " " << o->getEndTime() << std::endl;
}

I am debugging with 4 Outages into a vector, where I know the first is invalid and the rest of them valid. After executing the erase, the vector size is 3, so it looks ok. But if I iterate with the for loop to inspect the 3 Outages into the vector, the second one has been erased instead of the first.

I even debugged the isOutageValid method, and it is the first the only one who is returning false. Is there any mistake I'm missing?

Upvotes: 2

Views: 850

Answers (2)

Piotr Skotnicki
Piotr Skotnicki

Reputation: 48447

1.You forgot to specify the second argument of erase, which is the end of the range which is erased:

outages.erase(std::remove_if(outages.begin, outages.end(), isOutageValid), outages.end());

2.The condition is invalid, you should negate it:

 #include <functional>

 outages.erase(std::remove_if(outages.begin, outages.end(), std::not1(std::ptr_fun(&isOutageValid))), outages.end());

Upvotes: 4

Jarod42
Jarod42

Reputation: 217235

It should be:

outages.erase(std::remove_if(outages.begin, outages.end(), isNotOutageValid), outages.end());

Currently, you partition outages not valid first, valid last (in other words, your predicate is inverted).
And then remove the fist valid element (instead of a range).

Upvotes: 7

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