cairo by example

zeroable

The Cairo std library has some utilities for handling non zero values.

Here is how to get a NonZero<T> out of a felt252.

// The IsZeroResult<T> enum allows us to obtain a NonZero<T> via matching.
use zeroable::IsZeroResult;
use zeroable::NonZeroIntoImpl;

fn main() -> felt252 {
    // NonZeroIntoImpl converts a NonZero<T> into its inner value.
    NonZeroIntoImpl::into(felt_to_nonzero(1234))
}

fn felt_to_nonzero(value: felt252) -> NonZero<felt252> {
    // felt252_is_zero is a builtin method for felt252.
    match felt252_is_zero(value) {
        IsZeroResult::Zero(()) => panic(ArrayTrait::new()),
        IsZeroResult::NonZero(x) => x,
    }
}

Try it out!
  1. Install the toolchain:
    • For macOS and Linux, run our script:
      • curl -sL https://raw.githubusercontent.com/lambdaclass/cairo-by-example/main/build/installer.sh | bash -s 2.2.0
    • For Windows and others, please see the official guide
  2. Run the example:
    1. Copy the example into a zeroable.cairo file and run with:
      2. %!s(<nil>) zeroable.cairo

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