Crate kermit_parser 

Datalog query parser for Kermit.

Parses queries in the form Head :- Body1, Body2, ... . into a JoinQuery AST. Built on the winnow parser combinator library.

Syntax

• Variables start with an uppercase letter: X, Name
• Atoms (constants) start with a lowercase letter: alice, edge
• Placeholders are the anonymous wildcard _

path(X, Z) :- edge(X, Y), edge(Y, Z).

Example

use kermit_parser::{JoinQuery, Term};

let query: JoinQuery = "path(X, Z) :- edge(X, Y), edge(Y, Z)."
    .parse()
    .expect("valid Datalog");

assert_eq!(query.head.name, "path");
assert_eq!(query.head.terms, vec![
    Term::Var("X".into()),
    Term::Var("Z".into()),
]);
assert_eq!(query.body.len(), 2);
assert_eq!(query.body[0].name, "edge");

Parsing returns an error if the input is not a well-formed rule:

use kermit_parser::JoinQuery;

assert!("not a valid query".parse::<JoinQuery>().is_err());

Structs

JoinQuery

A parsed Datalog join query of the form Head :- Body1, Body2, ... .

Predicate

A Datalog predicate application, e.g. edge(X, Y).

Enums

Term

A single term in a Datalog predicate.