Overloaded oparators

[Li1]

Hi!
I don't undstand overloaded operators...can you explane how it works...somebody..
Thanks

[mbozzi]

The concept is pretty simple if you have some intuitive understanding of types.

A type is a definition. It defines a "type of thing". For example, int is a type that describes integers. Sure enough, part of C++'s definition says that we can add two ints together and get another int. This shouldn't be too surprising.

The interesting bit is that the words class and struct allow you to define your own types. For example, if you need to do math on two-dimensional vectors, it could be convenient to define them, by creating a new type named vec2. That type definition describes exactly what a vec2 is.

struct vec2 { // says: "every vec2 has an x and y position"
  float x, y; 
};

Maybe you need to compute their length, so you create a function to do that:

float len(vec2 v) { return std::sqrt(v.x * v.x + v.y * v.y); }

Which is how you say that len(v) is the length of v (where v is some vec2.)

Maybe you want to be able to add two vec2s together. We could create a function like this:

vec2 add(vec2 v1, vec2 v2) { return vec2{v1.x + v2.x, v1.y + v2.y }; }

Which is how you say that add(v1, v2) is the sum of v1 and v2 (where v1, v2 both have type vec2).

Unfortunately, we'd much rather be able to write v1 + v2 and mean the same thing. We can:

vec2& operator+=(vec2& l, vec2 r) { l.x += r.x, l.y += r.y; return l; }
vec2 operator+(vec2 l, vec2 r) { return l += r; }

Which is how you say that v1 + v2 is the sum of v1 and v2 (where v1, v2 both have type vec2).

[Li1]

Thanks

[gunnerfunner]

In addition to max's excellent summary, the following lecture notes might also be informative;
http://umich.edu/~eecs381/handouts/Operator_Overloading.pdf