Function parol::analysis::reachability::reachable_non_terminals [−][src]
Expand description
Calculates all reachable non-terminals.
use parol::{Cfg, Pr, Symbol};
use parol::analysis::reachable_non_terminals;
use std::collections::BTreeSet;
use std::convert::From;
let g = Cfg::with_start_symbol("S")
.add_pr(Pr::new("S", vec![Symbol::n("Y")]))
.add_pr(Pr::new("Y", vec![Symbol::n("Y"), Symbol::n("Z")]))
.add_pr(Pr::new("Y", vec![Symbol::n("Y"), Symbol::t("a", vec![0])]))
.add_pr(Pr::new("Y", vec![Symbol::t("b", vec![0])]))
.add_pr(Pr::new("U", vec![Symbol::n("V")]))
.add_pr(Pr::new("X", vec![Symbol::t("c", vec![0])]))
.add_pr(Pr::new("V", vec![Symbol::n("V"), Symbol::t("d", vec![0])]))
.add_pr(Pr::new("V", vec![Symbol::t("d", vec![0])]))
.add_pr(Pr::new("Z", vec![Symbol::n("Z"), Symbol::n("X")]));
let productive = reachable_non_terminals(&g);
assert_eq!(
[
"S".to_owned(),
"X".to_owned(),
"Y".to_owned(),
"Z".to_owned()
].iter().cloned().collect::<BTreeSet<String>>(),
productive);