gorf_blc2/
lib.rs

1use lambda_calculus::Term;
2pub fn le(a: usize) -> Box<dyn Iterator<Item = bool>>{
3    if a == 0{
4        return Box::new([true,false].into_iter());
5    }
6    let len = usize::BITS - a.leading_zeros();
7    let x = if len == 1{
8        vec![]
9    }else{
10        (0..len - 2).rev().map(|a|1 << a).map(|v|a & v != 0).collect()
11    };
12    return Box::new([true].into_iter().chain(le((len - 1) as usize)).chain(x.into_iter()));
13}
14pub fn encode(t: &Term) -> Box<dyn Iterator<Item = bool> + '_>{
15    match t{
16        Term::Var(v) => le(*v),
17        Term::Abs(term) => Box::new([false,false].into_iter().chain(encode(&*term))),
18        Term::App(t) => {
19            let (a,b) = t.as_ref();
20            Box::new([false,true].into_iter().chain(encode(a)).chain(encode(b)))
21        },
22    }
23}
24pub fn ld(a: &mut impl Iterator<Item = bool>) -> Option<usize>{
25    if !a.next()?{
26        return Some(0);
27    }
28    let mut x = 1;
29    let l = ld(a)?;
30    for _ in (0..l).rev(){
31        x = 2 * x + (if a.next()?{
32            1
33        }else{
34            0
35        })
36    };
37    return Some(x);;
38}
39pub fn decode(a: &mut impl Iterator<Item = bool>) -> Option<Term>{
40    match a.next()?{
41        true => Some(Term::Var(ld(a)?)),
42        false => match a.next()?{
43            false => Some(Term::Abs(Box::new(decode(a)?))),
44            true => Some(Term::App(Box::new((
45                decode(a)?,
46                decode(a)?
47            ))))
48        }
49    }
50}
gorf_blc2/lib.rs

gorf_blc2/
lib.rs
