cfg 0.10.1

Library for manipulating context-free grammars.
Documentation 
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#![cfg(feature = "cfg-classify")]

mod support;

use cfg::Cfg;
use cfg::classify::cyclical::Cycles;

#[test]
fn test_remove_cycles() {
    let mut cfg: Cfg = Cfg::new();
    let [start, a, b, c, d] = cfg.sym();

    cfg.rule(start)
        .rhs([a])
        .rule(a)
        .rhs([b])
        .rule(b)
        .rhs([c])
        .rule(c)
        .rhs([d])
        .rule(d)
        .rhs([a]);

    let mut equivalent: Cfg = Cfg::new();
    let [start, a] = equivalent.sym();

    // Order is significant.
    equivalent.rule(start).rhs([a]);
    {
        let mut cycles = Cycles::new(&mut cfg);
        let lhss: Vec<_> = cycles
            .cycle_participants(true)
            .map(|rule| rule.lhs)
            .collect();
        assert_eq!(lhss, &[a, b, c, d]);
        cycles.remove_cycles();
    };
    support::assert_eq_rules(equivalent.rules(), cfg.rules());
    assert!(Cycles::new(&mut cfg).cycle_free());
}

#[test]
fn test_rewrite_cycles() {
    let mut cfg: Cfg = Cfg::new();
    let [start, first, second] = cfg.sym();

    cfg.rule(start)
        .rhs([second])
        .rule(first)
        .rhs([second])
        .rule(second)
        .rhs([first]);

    let mut equivalent: Cfg = Cfg::new();
    let [start, first] = equivalent.sym();

    // Order is significant.
    equivalent.rule(start).rhs([first]);

    Cycles::new(&mut cfg).rewrite_cycles();
    support::assert_eq_rules(equivalent.rules(), cfg.rules());
    assert!(Cycles::new(&mut cfg).cycle_free());
}

#[test]
fn test_cycle_branch() {
    let mut cfg: Cfg = Cfg::new();
    let [start, a, b, c, d] = cfg.sym();

    cfg.rule(start)
        .rhs([a])
        .rule(a)
        .rhs([b])
        .rule(b)
        .rhs([c])
        .rule(c)
        .rhs([a])
        .rule(c)
        .rhs([d]);

    let mut equivalent: Cfg = Cfg::new();
    let [start, a, _, _, d] = equivalent.sym();

    // Order is significant.
    equivalent.rule(start).rhs([a]).rule(a).rhs([d]);
    {
        let mut cycles = Cycles::new(&mut cfg);
        let lhss: Vec<_> = cycles
            .cycle_participants(true)
            .map(|rule| rule.lhs)
            .collect();
        assert_eq!(lhss, &[a, b, c]);
        cycles.rewrite_cycles();
    };
    support::assert_eq_rules(equivalent.rules(), cfg.rules());
    assert!(Cycles::new(&mut cfg).cycle_free());
}