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# New to vectors, will this work correcty?

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I'm making a vector class and was wondering if my basic vector mathematics was right: The class declaration
class DFVector
{
public:
float x, y, z;

DFVector();
DFVector(float X, float Y, float Z);
DFVector(char cOperator, DFVector* vVector1, DFVector* vVector2); // this = vVector1 - vVector2

~DFVector();
D3DXVECTOR3 operator ()();
void operator =(DFVector pNewVector);
void operator +=(DFVector pPlusVector);
void operator -=(DFVector pMinusVector);
void operator ++();
void operator --();

};

And the definition

DFVector::DFVector()
{
x = y = z = 0.0f;
}

DFVector::DFVector(float X, float Y, float Z)
{
x = X;
y = Y;
z = Z;
}

DFVector::DFVector(char cOperator, DFVector* vVector1, DFVector* vVector2) // this = vVector1 - vVector2

{
switch(cOperator)
{
case '+':
{
x = vVector1->x + vVector2->x;
y = vVector1->y + vVector2->y;
z = vVector1->z + vVector2->z;
}

case '-':
{
x = vVector1->x - vVector2->x;
y = vVector1->y - vVector2->y;
z = vVector1->z - vVector2->z;
}

case '*':
{
x = vVector1->x * vVector2->x;
y = vVector1->y * vVector2->y;
z = vVector1->z * vVector2->z;
}

case '/':
{
x = vVector1->x / vVector2->x;
y = vVector1->y / vVector2->y;
z = vVector1->z / vVector2->z;
}
}
}

DFVector::~DFVector()
{
}

D3DXVECTOR3 DFVector::operator ()()
{
return D3DXVECTOR3(x, y, z);
}

void DFVector::operator =(DFVector pNewVector)
{
x = pNewVector.x;
y = pNewVector.y;
z = pNewVector.z;
}

void DFVector::operator +=(DFVector pPlusVector)
{
x += pPlusVector.x;
y += pPlusVector.y;
z += pPlusVector.z;
}

void DFVector::operator -=(DFVector pMinusVector)
{
x = pMinusVector.x;
y = pMinusVector.y;
z = pMinusVector.z;
}

void DFVector::operator ++()
{
x += 0.01f;
y += 0.01f;
z += 0.01f;
}

void DFVector::operator --()
{
x -= 0.01f;
y -= 0.01f;
z -= 0.01f;
}

Thanks for any advice! /* I use DirectX 8.1 and C++ (Microsoft Visual C++ 6.0 Professional edition) */ [edited by - Programmer16 on March 20, 2004 10:47:13 PM]

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dude, read some vector faq operator++ for vectors ? gosh. and try to use some const references...
and... where''s the vector math ? dot ? cross ?
oh... dont try to do your own vector math if ya have no idea how to cuz the d3dx can do it much faster than ya.
sorry for being rude - couldnt hold myself :>

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I said basic vector mathematics; dot and cross multiplication aren't basic vector math. I'm not using D3DX because I'm trying to learn vector math and you learn better by doing than by reading. I just added the ++ operator for something that I'm doing that needs to increase and decrease in all directions at once. And, what the difference make in using a const reference? I'm programming it so I know when I should/shouldn't modify code and when I'm supposed.

I'm testing it now, and its not working correctly for some reason:

DFVector g_dfVector(7,3,9);
DFVector g_dfVector2(2,6,5);
DFVector g_dfVector3('+', &g_dfVector, &g_dfVector2);

And then I print it to my log, and I get this:
g_dfVector g_dfVector2 g_dfVector3
X: 7.000000 - 2.000000 = 3.500000
Y: 3.000000 - 6.000000 = 0.500000
Z: 9.000000 - 5.000000 = 1.800000

/*
I use DirectX 8.1 and C++ (Microsoft Visual C++ 6.0 Professional edition)
*/

[edited by - Programmer16 on March 20, 2004 11:15:00 PM]

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I must admit that I haven''t looked the code completely through ... but if you would have tried it out it either doesn''t compile at all or you''ll get strange artefacts when testing it.

Two things I noticed:

the switch()-statement completely misses the "break;"s. even though you make nice blocks, the code won''t give you the results you want.
but after all, you might want to reconsider this system ... really no offense, maybe you do need it for some reason i can''t imagine, but i would design that without that switch statement (and passing the operation as char-parameter is something i wouldn''t do either), but never mind, i don''t know what you''re going to do with that...

Operator += (and similar) with a void type? If it even compiles ... I don''t know what you''re planning to do with that. Better check out a tutorial on operator overloading...

Oh yeah and the ++ / -- operators are really pointless in vector math (especially what you are doing with them ... the length of a vector is calculated by the sqrt of the sum of the squares of each component within the vector. i.e. sqrt(x*x+y*y+z*z). and if you intended to ++ the length of the vector, you''ll see that this won''t work...)

Hope it helped you a little!

Indeterminatus

--si tacuisses, philosophus mansisses--

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quote:

And then I print it to my log, and I get this:
g_dfVector g_dfVector2 g_dfVector3
X: 7.000000 - 2.000000 = 3.500000
Y: 3.000000 - 6.000000 = 0.500000
Z: 9.000000 - 5.000000 = 1.800000

THIS results from the the missing breaks. No matter what you do, you''ll always get the division (last case in the switch-statement). just add a "break;" at the end of each case-block and at least this should work out the way you want it.

But still - you should work on the operators, since they are pointless without return value...

Indeterminatus

--si tacuisses, philosophus mansisses--

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Ok, nevermind. I wasn't asking for advice on the class, I was asking for advice on the math since this is the math and physics forum.

The increment and decrement operators are for my current project and are for moving. Why do say my operators won't work? If I add g_dfVector3 += g_dfVector; It prints out 12,0,13 which is correct (7-2+7, 3-6+3, 9-5+9). Whats wrong with my overloaded constructor that uses the char? It I can instantly create a vector that is the result of any of the 4 basic operations without having four different functions.

/*
I use DirectX 8.1 and C++ (Microsoft Visual C++ 6.0 Professional edition)
*/

[edited by - Programmer16 on March 20, 2004 11:36:26 PM]

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quote:
Original post by Programmer16
I said basic vector mathematics; dot and cross multiplication aren''t basic vector math. I''m not using D3DX because I''m trying to learn vector math and you learn better by doing than by reading.

However, you need to read how to do things before you implement them. Dot and cross products are a fundamental part of vector mathematics. Go learn them. Now.

You have to remember that you''re unique, just like everybody else.

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I''m going to learn Dot and Cross, but I don''t know what they''re used for, so I''m just using basic operations in my current project.

/*
I use DirectX 8.1 and C++ (Microsoft Visual C++ 6.0 Professional edition)
*/

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Programmer16, you''re right, this is the math&physics forum. But even though you haven''t explicitly asked for it, I thought I should tell you that your code was buggy ... which will result in wrong results, speaking in mathematical terms. Never mind. And as for the operators: Don''t know where exactly it is (and frankly speaking I''m too lazy to look it up right now) specified, but it is somewhere in the c-standard that operators should return the result of the operation rather than void (which will allow for consistent usage of your code ... don''t forget that C/C++ is expression-based!)
And if they returned void, things like a = b = c = 10.0f; wouldn''t be possible.

Enough for today, now I really gotta go to bed ... nearly sunrise ... darn ... *fg* ...

Indeterminatus

--si tacuisses, philosophus mansisses--

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One word: DUH. I know my code is buggy. I'm trying to learn vectors and if I just use Direct3DX stuff I won't get anywhere. I haven't gotten anywhere actually. I didn't think about the situation that you pointed out about the operator. Would it be better to do this:
DFVector operator=(DFVector vVector)
{
x = vVector.x;
y = vVector.y;
z = vVector.z;
return (*this);
}
Thanks.
Sorry for getting pissy, I haven't slept in 26 hours.

/*
I use DirectX 8.1 and C++ (Microsoft Visual C++ 6.0 Professional edition)
*/

[edited by - Programmer16 on March 20, 2004 11:59:16 PM]

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