atan2 with CGPoint Iterator

Question

vector<CGPoint>::iterator i;
vector<CGPoint>* bp = bicyclePad.bikePathPoints;
for(i = bp->begin(); i != bp->end()-3; i++){
    angle = atan2((*i).y/(*i).x) * 180/ PI;
}

I guess atan2 can only be used with floats and doubles. but I am trying to do it with an iterator. How would I go about doing the above?

score 4 · Accepted Answer · answered Jan 06 '12 at 16:35

4

atan2 takes two arguments:

angle = std::atan2(i->y, i->x) * 180 / PI;

should work fine. The correct overload (depending on what CGFloat typedefs to) will be chosen.

Note that i->x and i->y (which are strictly equivalent to (*i).x and (*i).y) are numbers (of type CGFloat), not iterators.

answered Jan 06 '12 at 16:35

Alexandre C.

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And I'll just note here that the reason it takes two arguments is that if `i->y` is nonzero, `i->x` is *allowed to be zero* even though that would nominally create a divide by zero error. – Mark B Jan 06 '12 at 16:42
1

@MarkB: Also, `atan2(-1, -1) != atan2(1, 1)`. You get the full oriented angle of the vector `(x, y)` with `atan2`, and not just the inverse tangent of the quotient. – Alexandre C. Jan 06 '12 at 16:57

score 2 · Answer 2 · answered Jan 06 '12 at 16:36

2

This should work atan2(i->y, i->x) * 180 / PI

answered Jan 06 '12 at 16:36

Tony The Lion

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atan2 with CGPoint Iterator

2 Answers2