1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51

use std::fmt::Debug;

use crate::semirings::Semiring;
use crate::Tr;
use crate::EPS_LABEL;

/// Base trait to restrict which trs are traversed in an FST.
pub trait TrFilter<S: Semiring>: Clone + Debug + PartialEq {
    /// If true, Tr should be kept, else Tr should be ignored.
    fn keep(&self, tr: &Tr<S>) -> bool;
}

/// True for all trs.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct AnyTrFilter {}

impl<S: Semiring> TrFilter<S> for AnyTrFilter {
    fn keep(&self, _tr: &Tr<S>) -> bool {
        true
    }
}

/// True for (input/output) epsilon trs.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct EpsilonTrFilter {}

impl<S: Semiring> TrFilter<S> for EpsilonTrFilter {
    fn keep(&self, tr: &Tr<S>) -> bool {
        tr.ilabel == EPS_LABEL && tr.olabel == EPS_LABEL
    }
}

/// True for input epsilon trs.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct InputEpsilonTrFilter {}

impl<S: Semiring> TrFilter<S> for InputEpsilonTrFilter {
    fn keep(&self, tr: &Tr<S>) -> bool {
        tr.ilabel == EPS_LABEL
    }
}

/// True for output epsilon trs.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct OutputEpsilonTrFilter {}

impl<S: Semiring> TrFilter<S> for OutputEpsilonTrFilter {
    fn keep(&self, tr: &Tr<S>) -> bool {
        tr.olabel == EPS_LABEL
    }
}