Can't figure out how to print determinant

[its0x99]

I have been trying to print the determinant and I can't figure it out at all.

Main.cpp

#include <iostream>

#include "Mat3.h"

using namespace std;

int main()
{
	Mat3 a;
	Mat3 b;
	Mat3 c;

	Mat3 d;

	Vec3 v1(1, 2, 3);
	Vec3 v2;

	a.m[0] = 1;
	a.m[1] = 4;
	a.m[2] = 7;
	a.m[3] = 2;
	a.m[4] = 5;
	a.m[5] = 8;
	a.m[6] = 3;
	a.m[7] = 6;
	a.m[8] = 9;

	b.m[0] = 1;
	b.m[1] = 2;
	b.m[2] = 3;
	b.m[3] = 4;
	b.m[4] = 5;
	b.m[5] = 6;
	b.m[6] = 7;
	b.m[7] = 8;
	b.m[8] = 9;

	d.m[0] = 1;
	d.m[1] = 5;
	d.m[2] = 0;
	d.m[3] = 2;
	d.m[4] = 4;
	d.m[5] = 3;
	d.m[6] = 0;
	d.m[7] = 6;
	d.m[8] = 9;

	c = a * b;
	
	//Print Matrix
	cout << "Matrix a * b = \t" << endl;
	int i;
	for (i = 0; i < 9; i++)
	{
		if (i == 3 || i == 6)
		{
			cout << endl;
		}
		cout << c.m[i] << " ";
	}
	cout << endl;

	cout << "\n" << "Matrix a * v1 = \t";
	v2 = a * v1;
	//Print Vector
	cout << v2.x << "\t\t" << v2.y << "\t\t" << v2.z << "\n" << endl;

	//Print Determinant of d
	cout << "The determinant of d = \t";

	//d.Inverse();

	//Print Matrix

	getchar();
	return 0;
}

Mat3.cpp

#include "Mat3.h"

/* Matrix Constructor
	Set matrix entries to the identity matrix */
Mat3::Mat3()
{
	SetIdentity();
}

/* SetIdentity Member Function
	Set matrix entries to the identity matrix */
void Mat3::SetIdentity()
{
	int i;
	for (i = 0; i < 9; i++)
	{
		m[i] = 0;
	}
	m[0] = 1;
	m[4] = 1;
	m[8] = 1;
}

/* RotateZ Member Function
	Set matrix entries to the rotation matrix */
void Mat3::RotateZ(float angle)
{
	m[0] = cos(angle);
	m[1] = -sin(angle);
	m[2] = 0;
	m[3] = sin(angle);
	m[4] = cos(angle);
	m[5] = 0;
	m[6] = 0;
	m[7] = 0;
	m[8] = 1;
}

/* Scale Member Function
	Set matrix entries to the scale matrix */
void Mat3::Scale(float x, float y, float z)
{
	int i;
	for (i = 0; i < 9; i++)
	{
		m[i] = 0;
	}
	m[0] = x;
	m[4] = y;
	m[8] = z;
}

/* Transpose Member Function
	Set matrix entries to the transpose matrix */
void Mat3::Transpose()
{
	float temp;
	temp = m[1];
	m[1] = m[3];
	m[3] = temp;

	temp = m[2];
	m[2] = m[6];
	m[6] = temp;

	temp = m[7];
	m[7] = m[5];
	m[5] = temp;
}

/* Multiplication Member Function
	Calculate the multiplication of two matrices and return the result */
Mat3 Mat3::operator*(Mat3 otherMat)
{
	Mat3 tempM;
	tempM.m[0] = (m[0] * otherMat.m[0]) + (m[1] * otherMat.m[3]) + (m[2] * otherMat.m[6]);
	tempM.m[1] = (m[0] * otherMat.m[1]) + (m[1] * otherMat.m[4]) + (m[2] * otherMat.m[7]);
	tempM.m[2] = (m[0] * otherMat.m[2]) + (m[1] * otherMat.m[5]) + (m[2] * otherMat.m[8]);

	tempM.m[3] = (m[3] * otherMat.m[0]) + (m[4] * otherMat.m[3]) + (m[5] * otherMat.m[6]);
	tempM.m[4] = (m[3] * otherMat.m[1]) + (m[4] * otherMat.m[4]) + (m[5] * otherMat.m[7]);
	tempM.m[5] = (m[3] * otherMat.m[2]) + (m[4] * otherMat.m[5]) + (m[5] * otherMat.m[8]);

	tempM.m[6] = (m[6] * otherMat.m[0]) + (m[7] * otherMat.m[3]) + (m[8] * otherMat.m[6]);
	tempM.m[7] = (m[6] * otherMat.m[1]) + (m[7] * otherMat.m[4]) + (m[8] * otherMat.m[7]);
	tempM.m[8] = (m[6] * otherMat.m[2]) + (m[7] * otherMat.m[5]) + (m[8] * otherMat.m[8]);

	return tempM;
}

/* Matrix and Vector Multiplication Member Function
	Calculate the multiplication of a matrix and vector, and return the result */
Vec3 Mat3::operator*(Vec3 vector)
{
	float tempVec[3];

	tempVec[0] = (m[0] * vector.x) + (m[1] * vector.y) + (m[2] * vector.z);
	tempVec[1] = (m[3] * vector.x) + (m[4] * vector.y) + (m[5] * vector.z);
	tempVec[2] = (m[6] * vector.x) + (m[7] * vector.y) + (m[8] * vector.z);

	vector.x = tempVec[0];
	vector.y = tempVec[1];
	vector.z = tempVec[2];

	return vector;
}

/* Determinant Member Function
	Calculate the determinant of a matrix */
float Mat3::Det()
{
	float determinate;
	determinate = (m[0] * ((m[4] * m[8]) - (m[7] * m[5]))) - (m[1] * ((m[3] * m[8]) - (m[6] * m[5]))) + (m[2] * ((m[6] * m[2])));
	return determinate;
}

/* Inverse Member Function
	Calculate the inverse matrix 
void Mat3::Inverse()
{

}
*/

[Ganado]

The formatting thing is a known bug. You can edit your post and re-add the formatting by clicking the <> button or by typing in [code] and [/code] around your code now that the post has been made.

Can you explain more what the actual issue is? Is it calculating the determinate wrongly? What do you expect the determinant to be? What is the actual result?

I assume your matrix's format is:

m[0] m[1] m[2]
m[3] m[4] m[5]
m[6] m[7] m[8]

?

determinate = (m[0] * ((m[4] * m[8]) - (m[7] * m[5]))) - (m[1] * ((m[3] * m[8]) - (m[6] * m[5]))) + (m[2] * ((m[6] * m[2])));
Let's format that a bit,

determinate =
  m[0] * (m[4] * m[8] - m[7] * m[5])
- m[1] * (m[3] * m[8] - m[6] * m[5])
+ m[2] * m[6] * m[2];

What's going on with the third row there? Looks like a mistake to me.

[its0x99]

Yep fixed the formating issue

So the answer that I should get from the determinant is -72 but my problem is in main.cpp I can't figure out on how to actually print it in the console and yes my matrix format is

m[0] m[1] m[2]
m[3] m[4] m[5]
m[6] m[7] m[8]

Oh ye I missed one of them this is the fixed determinate:
determinate = (m[0] * ((m[4] * m[8]) - (m[7] * m[5]))) - (m[1] * ((m[3] * m[8]) - (m[6] * m[5]))) + (m[2] * ((m[3] * m[7]) - (m[6] * m[2])));

[Ganado]

So you mean you want to do this?
cout << "The determinant of d = \t" << d.Det() << endl;

[its0x99]

Yep that worked thank you. I have no clue why but sometimes my brain stops working and I can't find a simple answer

[ne555]

cout << d.Det();