pub trait Query<'a> {
fn query<Q: Reify + 'a>(
self,
query: Q
) -> Box<dyn Iterator<Item = Q::Reified> + 'a>;
}Expand description
Derive reified values potential resolved states.
Query is implemented for Goals and
States, meaning you can call
.query() on them with any type that implements
Reify.
This is a convenient wrapper around the common pattern of obtaining a StateIter, calling
.reify(query) on each state and returning only the
valid, fully resolved results. Query is implemented on a variety of
State related types, allowing it to be used in many
contexts.
A blanket impl covers anything that implements StateIterator, so many
types including Goal and State are
queryable.
Required Methods§
sourcefn query<Q: Reify + 'a>(
self,
query: Q
) -> Box<dyn Iterator<Item = Q::Reified> + 'a>
fn query<Q: Reify + 'a>(
self,
query: Q
) -> Box<dyn Iterator<Item = Q::Reified> + 'a>
Get reified results from things that can produce StateIters.
Examples:
Goals
use canrun::{Query, LVar};
use canrun::goals::unify;
let x = LVar::new();
let goal = unify(x, 1);
let result: Vec<_> = goal.query(x).collect();
assert_eq!(result, vec![1])State and Option<State>
Most of the lower level State update methods
return an Option<State>. Since StateIterator is implemented for
this type, Query is as well!
let state: Option<State> = State::new().unify(&x, &Value::new(1));
let result: Vec<_> = state.query(x).collect();
assert_eq!(result, vec![1])