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use crate::domains::Domain; use crate::state::IterResolved; use crate::ReifyIn; /** Derive [reified](crate::value::ReifyIn) [values](crate::value) potential resolved states. [Query] is implemented for [`Goals`](crate::goals) and [`States`](crate::State) (and other types), meaning you can call [`.query()`](Query::query()) on them with any type that implements [ReifyIn](crate::value::ReifyIn) for a matching [Domain]. This is a convenient wrapper around the pattern of iterating over a sequence of [`ResolvedStates`](crate::ResolvedState) and calling [`state.reify(query)`](crate::ResolvedState::reify()) and returning only the valid, fully resolved results. Query is implemented on a variety of [`State`](crate::State) related types, allowing it to be used in many contexts. A blanket impl covers anything that implements [`IterResolved`], so many types including [`Goal`](crate::goals) and [`State`](crate::State) are queryable. */ pub trait Query<'a, D: Domain<'a> + 'a> { /** Get [reified](crate::value::ReifyIn) results from an iterator of [`ResolvedStates`](crate::ResolvedState). # Examples: ## Goals ``` use canrun::{Goal, unify, var, State}; use canrun::example::I32; let x = var(); let goal: Goal<I32> = unify(x, 1); let result: Vec<_> = goal.query(x).collect(); assert_eq!(result, vec![1]) ``` ## States ``` use canrun::{State, IterResolved, Query, val, var}; use canrun::example::I32; let x = var(); let state: State<I32> = State::new(); let result: Vec<_> = state.query(x).collect(); assert_eq!(result, vec![]) // Nothing has been added to the State ``` ### `Option<State<D>>` Note that most of the lower level [`State`](crate::State) update methods return an `Option<State<D>>`. Since [`IterResolved`] is implemented for this type, Query is as well! ``` # use canrun::{State, IterResolved, Query, val, var}; # use canrun::example::I32; # let x = var(); let state: Option<State<I32>> = State::new().unify(&val!(x), &val!(1)); let result: Vec<_> = state.query(x).collect(); assert_eq!(result, vec![1]) ``` */ fn query<Q>(self, query: Q) -> Box<dyn Iterator<Item = Q::Reified> + 'a> where Q: ReifyIn<'a, D> + 'a; } impl<'a, D: Domain<'a> + 'a, S: IterResolved<'a, D>> Query<'a, D> for S { fn query<Q>(self, query: Q) -> Box<dyn Iterator<Item = Q::Reified> + 'a> where Q: ReifyIn<'a, D> + 'a, { Box::new( self.iter_resolved() .filter_map(move |resolved| query.reify_in(&resolved)), ) } }