Free Function (Helper)

A free function in Leo is a helper defined outside the program { } block. It is automatically inlined by the compiler into the calling function's proof rather than generating a separate proof of its own:

fn check_balance(balance: u64, amount: u64) -> bool {
    return balance >= amount;
}

program my_program.aleo {
    @noupgrade
    constructor() {}

    fn transfer(balance: u64, amount: u64) -> u64 {
        assert(check_balance(balance, amount));
        return balance - amount;
    }
}

Use free functions for code reuse - validation checks, calculations, formatting - without the overhead of creating additional transitions. They cannot be called directly from outside the program.