Function parol::analysis::reachability::reachable_from_production

pub fn reachable_from_production(cfg: &Cfg, prod_num: usize) -> BTreeSet<String>

Calculates for a given production all reachable non-terminals. Used for special derivation calculations (i.e. FOLLOW k relations)

use parol::{Cfg, Pr, Symbol};
use parol::analysis::reachable_from_production;
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_production(&g, 0);
assert_eq!(
    [
        "X".to_owned(),
        "Y".to_owned(),
        "Z".to_owned()
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 1);
assert_eq!(
    [
        "X".to_owned(),
        "Y".to_owned(),
        "Z".to_owned()
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 2);
assert_eq!(
    [
        "X".to_owned(),
        "Y".to_owned(),
        "Z".to_owned()
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 3);
assert_eq!(
    [
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 4);
assert_eq!(
    [
        "V".to_owned(),
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 5);
assert_eq!(
    [
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 6);
assert_eq!(
    [
        "V".to_owned(),
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 7);
assert_eq!(
    [
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);

let productive = reachable_from_production(&g, 8);
assert_eq!(
    [
        "X".to_owned(),
        "Z".to_owned()
    ].iter().cloned().collect::<BTreeSet<String>>(),
    productive);