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Home/ Questions/Q 9000791
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Editorial Team
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Editorial Team
Asked: June 16, 20262026-06-16T00:21:15+00:00 2026-06-16T00:21:15+00:00

Why does this code compile at all? #include <vector> using namespace std; class A

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Why does this code compile at all?

#include <vector>
using namespace std;

class A
{
        virtual void a() = 0;
};

int main()
{
        vector<A> a;    //won't fail
        //A b;            //that will
}
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  1. Editorial Team
    Editorial Team
    2026-06-16T00:21:16+00:00Added an answer on June 16, 2026 at 12:21 am

    Because templates. You don’t instanciate anything. Try using resize(), or some other method. That should fail.

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