Function parol::analysis::reachability::reachable_from_non_terminal
source · [−]Expand description
Calculates for a given non-terminal all reachable non-terminals. Used for special derivation calculations (i.e. FOLLOW k relations)
use parol::{Cfg, Pr, Symbol};
use parol::analysis::reachable_from_non_terminal;
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_n("a", vec![0])]))
.add_pr(Pr::new("Y", vec![Symbol::t_n("b", vec![0])]))
.add_pr(Pr::new("U", vec![Symbol::n("V")]))
.add_pr(Pr::new("X", vec![Symbol::t_n("c", vec![0])]))
.add_pr(Pr::new("V", vec![Symbol::n("V"), Symbol::t_n("d", vec![0])]))
.add_pr(Pr::new("V", vec![Symbol::t_n("d", vec![0])]))
.add_pr(Pr::new("Z", vec![Symbol::n("Z"), Symbol::n("X")]));
let productive = reachable_from_non_terminal(&g, "S");
assert_eq!(
[
"X".to_owned(),
"Y".to_owned(),
"Z".to_owned()
].iter().cloned().collect::<BTreeSet<String>>(),
productive);
let productive = reachable_from_non_terminal(&g, "U");
assert_eq!(
[
"V".to_owned(),
].iter().cloned().collect::<BTreeSet<String>>(),
productive);
let productive = reachable_from_non_terminal(&g, "Y");
assert_eq!(
[
"X".to_owned(),
"Y".to_owned(),
"Z".to_owned()
].iter().cloned().collect::<BTreeSet<String>>(),
productive);
let productive = reachable_from_non_terminal(&g, "X");
assert_eq!(
[
].iter().cloned().collect::<BTreeSet<String>>(),
productive);
let productive = reachable_from_non_terminal(&g, "Z");
assert_eq!(
[
"X".to_owned(),
"Z".to_owned()
].iter().cloned().collect::<BTreeSet<String>>(),
productive);