Functions that return a struct

• Function that returns both roots of a second degree polynomial equation:

/* Struct to store two values */
struct roots {
    float x1, x2;
};

/* Function that receives the coefficients a, b and c and returns the roots of the second degree polynomial 
(it doesn't cover the case of a negative delta) */
struct roots Quadratic (int a, int b, int c) {
    struct roots x;
    float delta;

    delta = b*b - 4*a*c;

    x.x1 = (-b + sqrt(delta))/(2*a);
    x.x2 = (-b - sqrt(delta))/(2*a);

    return x;
}

Functions can also be of 'struct' type and return a 'struct', much like a function that returns an integer or a float. Inside the function "Quadratic" we have to declare a variable of the same struct type to store both roots.

The syntax of 'roots' includes curly brackets, but it's a struct, not a function. That's why it ends with a semi-colon.

Note: the function is not returning two variables. It's returning the values stored in the struct "x", which type's "roots".

• Calling the above function:

/* 1st way */
printf("%f, %f", Quadratic(1, 2, -3).x1, Quadratic(1, 2, -3).x2);

/* 2nd way*/
struct roots x;
x = Quadratic(1, 2, -3);
printf("%f, %f", x.x1, x.x2);

Both should produce the same result: print the roots -3 and 1.