Reference

[RenderMan]

I am trying to learn how pointers work :)
This code work's perfectly:

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#include <iostream> using namespace std; void offsetvector(double &x0, double &y0, double &x1, double &y1, double offsetX, double offsetY) { x0 += offsetX; x1 += offsetX; y0 += offsetY; y1 += offsetY; } void printvector(double x0, double y0, double x1, double y1) { cout << "(" << x0 << "," << y0 << ") -> (" << x1 << "," << y1 << ")" << endl; } int main() { double xStart = 2.1; double yStart = 2.2; double xEnd = 4.1; double yEnd = 4.2; offsetvector(xStart, yStart, xEnd, yEnd, 1.0, 1.5); printvector(xStart, yStart, xEnd, yEnd); }

But if i change offsetvector function to this: ... &x0 += offsetX; &x1 += offsetX; &y0 += offsetY; &y1 += offsetY; ... or &y1 = 20.0; or &y1 = &y0;

it doesn't work. Why?

[kooth]

You are actually using references (which is the preferred method of argument passing.) When you change offsetvector() to this:

&x0 += offsetX;

You are adding the value of offsetX to the address of x0, which I don't think will even compile. Your initial version has it correctly.

[RenderMan]

Thanks kppth for your fast response.

Yes, i understand that. Thanks.

But why this does not work?

&y1 = &y0;

actually making the address of y0 same as y1.

PS: Writing this I actually figure it out that you cannot have 2 values in the same address.
( this could be the reason:) )

[Fransje]

Writing this I actually figure it out that you cannot have 2 values in the same address.

That's exactly right. 2 values at the same address means 2 variables at one memory location, which is inpossible, there simply is no space to do that.