stak_native/
list.rs

1use stak_vm::{Error, Memory, PrimitiveSet, Type};
2
3/// A list primitive.
4pub enum ListPrimitive {
5    /// An `assq` procedure.
6    Assq,
7    /// A `cons` procedure.
8    Cons,
9    /// A `memq` procedure.
10    Memq,
11}
12
13impl ListPrimitive {
14    const ASSQ: usize = Self::Assq as _;
15    const CONS: usize = Self::Cons as _;
16    const MEMQ: usize = Self::Memq as _;
17}
18
19/// A list primitive set.
20#[derive(Debug, Default)]
21pub struct ListPrimitiveSet {}
22
23impl ListPrimitiveSet {
24    /// Creates a primitive set.
25    pub fn new() -> Self {
26        Self::default()
27    }
28}
29
30impl PrimitiveSet for ListPrimitiveSet {
31    type Error = Error;
32
33    fn operate(&mut self, memory: &mut Memory, primitive: usize) -> Result<(), Self::Error> {
34        match primitive {
35            ListPrimitive::ASSQ => {
36                let [x, xs] = memory.pop_many();
37                let mut xs = xs.assume_cons();
38                let mut y = memory.boolean(false);
39
40                while xs != memory.null() {
41                    let cons = memory.car(xs).assume_cons();
42
43                    if x == memory.car(cons) {
44                        y = cons;
45                        break;
46                    }
47
48                    xs = memory.cdr(xs).assume_cons();
49                }
50
51                memory.push(y.into())?;
52            }
53            ListPrimitive::CONS => {
54                let [car, cdr] = memory.pop_many();
55
56                let rib = memory.allocate(car, cdr.set_tag(Type::Pair as _))?;
57                memory.push(rib.into())?;
58            }
59            ListPrimitive::MEMQ => {
60                let [x, xs] = memory.pop_many();
61                let mut xs = xs.assume_cons();
62                let mut y = memory.boolean(false);
63
64                while xs != memory.null() {
65                    if x == memory.car(xs) {
66                        y = xs;
67                        break;
68                    }
69
70                    xs = memory.cdr(xs).assume_cons();
71                }
72
73                memory.push(y.into())?;
74            }
75            _ => return Err(Error::IllegalPrimitive),
76        }
77
78        Ok(())
79    }
80}
stak_native/list.rs

stak_native/
list.rs
