Not

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Overview

To create a rule that is only satisfied when a specific rule is not met, you can use the Not Rule Composer. This composer allows you to negate the result of another rule.

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Example

For example, let’s consider a case where we only allow all numbers except 50.

type Target = Refined<Not<EqualRuleU8<50>>>;

In this example, the Target type is defined as a refined type that only accepts numbers except 50.

Let’s see how this rule works in practice.

fn not_example() -> Result<(), Error<u8>> {
    let target = Target::new(49)?;
    assert_eq!(target.into_value(), 49);

    let target = Target::new(50);
    assert!(target.is_err());

    let target = Target::new(51)?;
    assert_eq!(target.into_value(), 51);

    Ok(())
}