How to determine if 2 points in 2D space make right triangle?

[Putarda]

So I'm making calculateDistance function and I don't know how to determine if two points of an object make an right triangle.
Here is my code:

	float ObjectManager::calculateDistance(ls::Object* object, ls::Object* second_object) {

		float a = (object->getPosition()->x - second_object->getPosition()->x) * (object->getPosition()->x - second_object->getPosition()->x)
			, b = (object->getPosition()->y - second_object->getPosition()->y) * (object->getPosition()->y - second_object->getPosition()->y), c = a - b;

		if (c < 0) c *= -1;

		return sqrt(c);
	}

[keskiverto]

What is a "right triangle"?

How do you get a triangle from two points?

[Putarda]

object->setPosition(0,0);
second_object->setPosition(50,50);

std::cout << calculateDistance(object, second_object);
//prints 0

[mbozzi]

Assuming the third point is the origin -- take the inner product of the two vectors. The two vectors are orthogonal if and only if their inner product is zero.

Let
u = <x₁, y₁>, v = <x₂, y₂>:
<x₁, y₁> * <x₂, y₂> = x₁x₂ * y₁y₂ = ||u|| ||v|| cos(t) = 0 |_{(t = pi / 2)}

Orthogonality (or "making a right triangle") is not a requirement to compute distance between two points. Points cannot be orthogonal.
To get the distance:

const auto x1 = object->getPosition()->x, x2 = second_object->getPosition()->x;
const auto y1 = object->getPosition()->y, y2 = second_object->getPosition()->y;
const auto delta_x = x2 - x1, delta_y = y2 - y1;
return std::sqrt(delta_x * delta_x + delta_y * delta_y);