Function query 

pub fn query(
    cx: &mut Cx,
    db: &LogicDb,
    config: &LogicConfig,
    goal: Expr,
) -> Result<LogicStream>

Resolves goal against db and returns the answers as a logic stream.

Resolution is bounded by config; the answer count is capped at config.limits.max_answers.

Examples

use std::sync::Arc;
use sim_kernel::{Cx, DefaultFactory, EagerPolicy, Expr, Symbol};
use sim_lib_logic::{LogicConfig, LogicDb, query};

let mut cx = Cx::new(Arc::new(EagerPolicy), Arc::new(DefaultFactory));
let mut db = LogicDb::new();
db.assert_clause_expr(Expr::List(vec![
    Expr::Symbol(Symbol::new("fact")),
    Expr::List(vec![
        Expr::Symbol(Symbol::new("parent")),
        Expr::Symbol(Symbol::new("alice")),
        Expr::Symbol(Symbol::new("bob")),
    ]),
]))
.unwrap();

let goal = Expr::List(vec![
    Expr::Symbol(Symbol::new("parent")),
    Expr::Symbol(Symbol::new("alice")),
    Expr::Local(Symbol::new("who")),
]);
let stream = query(&mut cx, &db, &LogicConfig::default(), goal).unwrap();
let answers = stream.collect(&mut cx, None).unwrap();
assert_eq!(answers.len(), 1);