Shortest way to calculate difference between two numbers?

Question

I'm about to do this in C++ but I have had to do it in several languages, it's a fairly common and simple problem, and this is the last time. I've had enough of coding it as I do, I'm sure there must be a better method, so I'm posting here before I write out the same long winded method in yet another language;

Consider the (lilies!) following code;

// I want the difference between these two values as a positive integer int x = 7 int y = 3 int diff; // This means you have to find the largest number first  // before making the subtract, to keep the answer positive if (x>y) {       diff = (x-y); } else if (y>x) {      diff = (y-x); } else if (x==y) {     diff = 0; } 

This may sound petty but that seems like a lot to me, just to get the difference between two numbers. Is this in fact a completely reasonable way of doing things and I'm being unnecessarily pedantic, or is my spidey sense tingling with good reason?

Answer 1

Just get the absolute value of the difference:

#include <cstdlib> int diff = std::abs(x-y); 

Answer 2

Using the std::abs() function is one clear way to do this, as others here have suggested.

But perhaps you are interested in succinctly writing this function without library calls.

In that case

diff = x > y ? x - y : y - x; 

is a short way.

In your comments, you suggested that you are interested in speed. In that case, you may be interested in ways of performing this operation that do not require branching. This link describes some.