cairo by example


To store data in variables with the let keyword but you will not be able to change the value of said variables.

if you need to change that data, it must be a mutable variable with let mut

fn main() {
    let immutable_var: felt252 = 17;
    // immutable_var = 38;  <-- fails to compile

    // but this is legal:
    let mut mutable_var: felt252 = immutable_var;
    mutable_var = 38;

    assert(mutable_var != immutable_var, 'mutable equals immutable');

fn test_main() {

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 variables.cairo file and run with:
    2. %!s(<nil>) variables.cairo

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