declared variable as float, but output is coming in integers

Question

I have written a program using Xlib headers in c++ This is a part of it.

XPoint m[5];

m[0].x = 0; m[0].y = 400;
m[1].x = 150; m[1].y = 250;
m[2].x = 250; m[2].y = 300;
m[3].x = 300; m[3].y = 200;
m[4].x = 450; m[4].y = 400;

float slope=(m[2].y-m[1].y)/(m[2].x-m[1].x); cout<<slope<<endl; 

slope should be 0.5 but it gives 0. Can you please explain why and what's the correct way?? Is it because of the XPoint?? Help is greatly appreciated.

Answer 1

It seems the members x and y are of an integral type, so the division is done on integers, which simply truncates the fractional part of the result. In other words, 50 / 100, which is 0.5, gets truncated to the 0 you see in your output.

In order to avoid that, you must cast one of the operands to a floating point value, like this:

float slope = static_cast<float>(m[2].y-m[1].y)/(m[2].x-m[1].x);