cairo by example


A function is a unit of code that performs some logic. It is defined using the fn keyword.

Examples of functions are:

// This functions doesn't return anything.
fn main() {
    let x = 3;

// This function returns an u32.
fn inc(x: u32) -> u32 {
    x + 1

The Cairo convention is to name functions using the ‘snake_case’ form. In the example above, the function name is inc_n.

Note that in Cairo, functions always return a value. When the function has no particular return value, it is common to return the unit type (()).

Try it out!
  1. Install the toolchain:
    • For macOS and Linux, run our script:
    • curl -sL | bash -s 2.2.0
    • For Windows and others, please see the official guide
  2. Run the example:
    1. Copy the example into a functions.cairo file and run with:
    2. %!s(<nil>) functions.cairo

prev (variables) next (named parameters)