CODEWITHSUNDEEP
c++bit-manipulation
cool mr croc
cool mr croc

Reputation: 725

Using bitwise or equals (|= with a vector

I can't do the following, compiler says no matching operator in std::vector and I don't think I can overload it. So what are my options, apart from only using the 1 vector to store collision results. I'm trying to be extremely cache friendly and I don't want the same bool reset back to false after its been set to true, hence the or.

void CollisionDetection(const vector<Vector2D>& position1, 
                        const vector<Vector2D>& position2,
                        dimension dim1, dimension dim2, 
                        vector<bool>& result1, vector<bool>& result2)
{
    assert(position1.size()==result1.size());
    assert(position2.size()==result2.size());

    for(int i=0;i<position1.size();i++)
    {
        for(int j=0;j<position2.size();j++)
        {
            result1[i] |= result2[i] |= 
            rectOverlap(position1[1], position2[i], dim1, dim2);
        }
    }
}

Upvotes: 0

Views: 1611

Answers (2)

djechlin
djechlin

Reputation: 60778

Never use vector<bool>. Yes, I expect bitwise operators to fail miserably on this type.

See e.g. Alternative to vector<bool>

Upvotes: 3

mfontanini
mfontanini

Reputation: 21900

std::vector<bool> is a specialization of a std::vector. This specialization saves space by using 1 bit for each bool, instead of 1 byte.

std::vector<bool>::operator[] returns a reference wrapper(in order to allow this space-save optimization), which apparently does not implement operator|.

Upvotes: 3

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