Trait Predicate

pub trait Predicate<Item: ?Sized>: PredicateReflection {
    // Required method
    fn eval(&self, variable: &Item) -> bool;

    // Provided method
    fn find_case<'a>(
        &'a self,
        expected: bool,
        variable: &Item,
    ) -> Option<Case<'a>> { ... }
}

Trait for generically evaluating a type against a dynamically created predicate function.

The exact meaning of eval depends on the situation, but will usually mean that the evaluated item is in some sort of pre-defined set. This is different from Ord and Eq in that an item will almost never be the same type as the implementing Predicate type.

Required Methods

fn eval(&self, variable: &Item) -> bool

Execute this Predicate against variable, returning the resulting boolean.

Provided Methods

fn find_case<'a>(&'a self, expected: bool, variable: &Item) -> Option<Case<'a>>

Find a case that proves this predicate as expected when run against variable.

Implementors