C++ :: Using Structs To Define A Function

What I'm trying to do :

struct foo {int x; int y;};
foo function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}

Works as is, however when I try doing it through seperate class files :

//header file for class example_class
struct foo {int x; int y;};
foo function_example(int x, int y);

//source file for example_class
foo example_class::function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}

I get an error telling me that foo is undefined, and that declaration of function_example(int x, int y) is incompatible with the declaration of it in the header file.