| // Copyright (c) 2018 The predicates-rs Project Developers. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use crate::reflection; |
| |
| /// 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. |
| pub trait Predicate<Item: ?Sized>: reflection::PredicateReflection { |
| /// Execute this `Predicate` against `variable`, returning the resulting |
| /// boolean. |
| fn eval(&self, variable: &Item) -> bool; |
| |
| /// Find a case that proves this predicate as `expected` when run against `variable`. |
| fn find_case<'a>(&'a self, expected: bool, variable: &Item) -> Option<reflection::Case<'a>> { |
| let actual = self.eval(variable); |
| if expected == actual { |
| Some(reflection::Case::new(None, actual)) |
| } else { |
| None |
| } |
| } |
| } |
