specification-core

specification-core is the synchronous, dependency-conscious Rust foundation for composable business rules based on the Specification Pattern. A Specification<T> evaluates a borrowed T; closures work directly as specifications and the and, or, and not methods construct statically dispatched, allocation-free rules.

use specification_core::Specification;

let is_positive = |value: &i32| *value > 0;
assert!(is_positive.is_satisfied_by(&1));