Thread: Code compiling but not working!

This program is to find the area of a triangle using three vertices. It compiles but I get these warnings in the main function:
37:21: warning: variable 'aTriangle' set but not used [-Wunused-but-set-variable]45:7: warning: 'area' is used uninitialized in this function [-Wuninitialized]

I get the first one at the struct triangle aTriangle declaration and the second at cout area. The output is 0. I don't understand why.

Code:

//-----Include required headers here-----
#include<iostream>
#include<cmath>
using namespace std;
//-----End of headers-----


//-----Don't change/delete structs-----
struct vertex{
   float x;
   float y;
};


struct triangle{
    vertex vertices[3];
};
//-----Structs end here




//-----Add new functions here(if any)-----


//-----New functions end here-----


float cal_area(triangle aTriangle) {
    //Write your solution below this line
    float s,area,a,b,c;
    a=sqrt(pow((aTriangle.vertices[1].x-aTriangle.vertices[2].x),2)-pow((aTriangle.vertices[1].y-aTriangle.vertices[2].y),2));
    b=sqrt(pow((aTriangle.vertices[2].x-aTriangle.vertices[3].x),2)-pow((aTriangle.vertices[2].y-aTriangle.vertices[3].y),2));
    c=sqrt(pow((aTriangle.vertices[1].x-aTriangle.vertices[3].x),2)-pow((aTriangle.vertices[1].y-aTriangle.vertices[3].y),2));
    s=0.5*(a+b+c);
    area=sqrt(s*(s-a)*(s-b)*(s-c));
    return (area);
    //Dont write below this line
}
int main()
{
    struct triangle aTriangle;
    aTriangle.vertices[1].x=1;
    aTriangle.vertices[2].x=2;
    aTriangle.vertices[3].x=5;
    aTriangle.vertices[1].y=4;
    aTriangle.vertices[2].y=5;
    aTriangle.vertices[3].y=20;
    float cal_area(triangle aTriangle);
cout<<area<<endl;
    return 0;
}

Originally Posted by Abhishek Suresh

Code compiling but not working!

Are you sure about that ?

Originally Posted by Abhishek Suresh

Code:

    struct triangle aTriangle;

You don't need to explicitly write that just

Code:

triangle aTriangle;

Is enough. This is not C, in C++ struct declarations are similar to class declarations.

Originally Posted by Abhishek Suresh

Code:

 aTriangle.vertices[3].y=20;

This is not correct, array indices start from 0 which means with the 3 elements in the array the last element has index 2 not 3.

I have corrected the array indices so now they go from 0 to 2.

I also added a variable float answer in the main function, and wrote
answer=cal_area(triangle aTriangle);
cout<<answer<<endl;
but I get this error:
main.cpp:50:30: error: expected primary-expression before 'aTriangle'
answer=cal_area(triangle aTriangle);

Google gives me other cases of this errror but not before a variable like this.

For function calls, just the name of the argument is enough here.

Code:

answer=cal_area(aTriangle);

Thank you all! There was another error in the formula I used and I corrected it, it works now.