Triangle class, verify before instantiate the objects if possible to define a triangle

Question

The if loop doesn't work and i don't know how to fix it, i have to verify the entered numbers read from the KBD to see if they can form a triangle, but it's not working as it should.. I wrote the code in Visual Studio 2019, separately in a header file and a source file.

#include<iostream>
using namespace std;

class Triangle
{
protected:
    int a, b, c;
public:
    Triangle(int x = 0, int y = 0, int z = 0)
    {
        a = x;
        b = y;
        c = z;
    }
    float perim()
    {
        return (a + b + c) / 2;
    }
};

class Triangle_extended :public Triangle //derived class in public method
{
public:
    Triangle_extended(int x, int y, int z) :Triangle(x, y, z) {}
    float area()
    {
        float p;
        p = perim();
        return sqrt(p * (p - a) * (p - b) * (p - c));
    }
};

The problem looks like is in the main(), but i don't know where Also, when i use ob1 to find the perimeter, it gives 0 all the time, if i use ob2 for that too it gives the correct value. I have to make it work with object 1

#include"Header.h"

int main()
{
    int a, b, c;
    Triangle ob1; //object for the base class
    cout << "Enter 3 sides:";
    cin >> a >> b >> c;

    if ((a + b > c) || (a + c > b) || (b + c > a))
    {
        Triangle_extended ob2(a, b, c); //object for the derived class
        cout << "\nPerimeter is:" << ob1.perim();
        cout << "\nArea is:" << ob2.area();
    }
    else
        cout << "\nNumbers can't form a triangle!";

}

`Triangle::perim` will always return an integer, rewrite it this way for example: `(a + b + c) / 2.0;` https://stackoverflow.com/q/12447325/3365922 — fas, May 14 '20 at 08:58
So, you've showed the working code. If you want help with code then you should show the code that isn't working. — john, May 14 '20 at 08:58
Where did you entered the values `a` `b` `c` into `ob1` ? seems like `ob1` set to 0 in the constructor and you never updated those values — dt170, May 14 '20 at 08:58
if `a`, `b`, `c` are sides of triangle, why perimeter have `/ 2`. call it semi-perimeter, or do the division in Area method. — Jarod42, May 14 '20 at 09:30
@Jarod42 yeah,you're right, i put the division in area() method. Thank you — vivi25-5, May 14 '20 at 10:20
@dt170 yes, that was the problem, now everything's ok. thank you ! — vivi25-5, May 14 '20 at 10:27
@vivi25-5 Glad to hear that I added it as an answer so you may mark it and others will see — dt170, May 14 '20 at 11:00

score 1 · Answer 1 · answered May 14 '20 at 10:36

You can just pass on the values of a,b and c to the Triangle constructor via ob1, i.e,

cout << "Enter 3 sides:";
cin >> a >> b >> c;
 Triangle ob1(a,b,c);

that's it. Also, you can do p = perim()/2 in the area() method as perimeter is just the sum of all sides.So, no need to do return (a + b + c)/2; in the perim() method.

dt170 · Accepted Answer · 2020-05-14T11:04:54.827

Where did you entered the values a b c into ob1 ?

#include"Header.h"

int main()
{
    int a, b, c;
    Triangle ob1; //object for the base class
    cout << "Enter 3 sides:";
    cin >> a >> b >> c;

You can either use setter to do so or just change it into

#include"Header.h"

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

    cout << "Enter 3 sides:";
    cin >> a >> b >> c;
    Triangle ob1(a,b,c); 
    .
    .
    .
 }

Triangle class, verify before instantiate the objects if possible to define a triangle

2 Answers2