Crate logic_eval

Expand description

§logic-eval

A simple logic evaluator.

§Example

use logic_eval::{Database, parse_str, intern::DroplessInterner};

// Creates a DB.
let interner = DroplessInterner::default();
let mut db = Database::new(&interner);
let dataset = "
    child(a, b).
    child(b, c).
    descend($X, $Y) :- child($X, $Y).
    descend($X, $Z) :- child($X, $Y), descend($Y, $Z).
";
db.insert_dataset(parse_str(dataset, &interner).unwrap());
db.commit();

// Queries the DB.
let query = "descend($X, $Y).";
let mut cx = db.query(parse_str(query, &interner).unwrap());

let mut answer = Vec::new();
while let Some(eval) = cx.prove_next() {
    let s = eval.into_iter().map(|assign| assign.to_string()).collect::<Vec<_>>().join(", ");
    answer.push(s);
}

assert_eq!(answer, [
    "$X = a, $Y = b",
    "$X = b, $Y = c",
    "$X = a, $Y = c",
])