//preprocessor directives
#include <iostream>
#include <cmath>             // needed for using abs() function
using namespace std;

// function prototypes
double ComputeTriangleArea (double length, double width);
void OutputComputeAbsoluteDifference (double area1, double area2);

// main function
int main()
{
    // Parameter Declarations
    double width1, width2, length1, length2;
    double area1, area2;
    
    // LOGO
    cout << "----------------------------------------------------------" << endl;
    cout << "       CS135 Lab Quiz 2: Area Difference Computation      " << endl;
    cout << "                        By Chang Jia                      " << endl;
    cout << "----------------------------------------------------------" << endl;
    cout << endl;
     
    // Get Inputs
    cout << "Please enter the length of the first triangle: ";
    cin >> length1;
    cout << "Please enter the width of the first triangle: ";
    cin >> width1;
    cout << "Please enter the length of the second trianle: ";
    cin >> length2;
    cout << "Please enter the width of the second trianle: ";
    cin >> width2;
    cout << endl;
    
    // Do computations by calling functions
    area1 = ComputeTriangleArea(length1, width1);
    area2 = ComputeTriangleArea(length2, width2);    
    
    // Print Outputs
    cout << "The area of the first triangle is: " << area1 << endl;
    cout << "The area of the second trianle is: " << area2 << endl;
    cout << "The absolute difference of the two triangles is: ";
    OutputComputeAbsoluteDifference (area1, area2);
    cout << endl;
     
    system("PAUSE");
    return 0;
}

//function bodies
//function to compute area of triangle
double ComputeTriangleArea (double length, double width)
{
       double area_of_triange;
       area_of_triange = length * width / 2.0;     
       return area_of_triange;
}

//funtion to compute absolute difference of the two areas
void OutputComputeAbsoluteDifference (double area1, double area2)
{
       double difference;
       // Use abs() function 
       difference = abs(area1 - area2);
       cout << difference;
       return;
}
    
/* Test Run:
        
----------------------------------------------------------
       CS135 Lab Quiz 2: Area Difference Computation
                        By Chang Jia
----------------------------------------------------------

Please enter the length of the first triangle: 3
Please enter the width of the first triangle: 4
Please enter the length of the second trianle: 5
Please enter the width of the second trianle: 5

The area of the first triangle is: 6
The area of the second trianle is: 12.5
The absolute difference of the two triangles is: 6.5
Press any key to continue . . .

*/