Lesson 12.4. Structures and functions

Structures, as well as variables, can be passed as parameters in functions:

call by value
call by reference

Call by value

When a structure is called by value in a function, its content is copied locally into the function, as for variables.

// Call by value
void fct (struct vector v);

If a function has to modify the content of a structure, a call by reference must be used.

Call by reference

As for variables, passing a structure pointer as a parameter to a function allows it to access its contents in read and write mode.

// Call by reference
void fct (struct vector * v);

Note that in the case of a structure pointer, the fields are accessible with the -> operator:

// x field of the structure pointer v
v->x

Exercises

Exercise 1

Create a vector structure that contains the coordinates of a vector in 3 dimensions. Write a function norm() that receives a vector as a parameter and returns the norm (length) of the vector.

Here is an example of how to calculate the norm:

x=2.3
y=3.4
z=4.5
The norm of the vector is : 6.090977

Do the exercise

Solution

Exercise 2

Create a RGB structure that contains three colors (red, green and blue) and a grey value. Write a grayscale() function that computes and updates the grey field of the structure by averaging the three colors.

$$ grey = \dfrac{red+green+blue}{3} $$

Here is an example:

R = 120
G = 180
B = 64
---------------
Grey = 121

Do the exercise

Solution

Quiz

Why is there no real question in this quiz?

I've lost my inspiration

it's late and I'm hungry

I am tired

what's the point anyway? You already know everything!

Check

Lesson 12.3 Summary Lesson 13.1