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
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
// A partial Scheme implementation in Rust
// Build with: rustc minimal.rs -o minimal-rust
use std::io;
use std::io::Write;
// There doesn't seem to be a symbole or quote type in Rust, so i'm going to use strings and
// vectors
// "list of tokens" implemented as a vector of String.
// AST implemented as nested tuples (immutable).
//let const SCHEME_BUILTINS = ("lambda", "quote", "cond", "else", "cons", "car", "cdr", "null?", "eq?", "atom?", "zero?", "number?", "+", "-", "*", "/");
#[allow(dead_code)]
enum SchemeAtom<'a> {
SchemeNull,
SchemeTrue,
SchemeFalse,
SchemeNum(f64),
SchemeBuiltin(&'a str),
SchemeStr(&'a str),
}
enum SchemeExpr<'a> {
SchemeAtom(SchemeAtom<'a>),
SchemeList(Vec<SchemeExpr<'a>>),
}
///////////////////////////////////
fn is_zero(n: f64) -> bool {
return n == 0.;
}
///////////////////////////////////
fn scheme_tokenize(s: &String) -> Result<Vec<&String>, &'static str> {
let ret = vec![s];
return Ok(ret);
}
fn scheme_parse_num(s: &String) -> Result<f64, &'static str> {
let num = 0.;
return Ok(num);
}
fn scheme_parse_sexpr(sexpr: Vec<&String>) -> Result<SchemeExpr, &'static str> {
let ret = sexpr.into_iter().map(|el| SchemeExpr::SchemeAtom(SchemeAtom::SchemeStr(el))).collect();
return Ok(SchemeExpr::SchemeList(ret))
}
fn scheme_parse(tokens: SchemeExpr) -> Result<SchemeExpr, &'static str> {
return Ok(SchemeExpr::SchemeAtom(SchemeAtom::SchemeNull));
}
fn scheme_eval(ast: SchemeExpr) -> Result<SchemeExpr, &'static str> {
return Ok(SchemeExpr::SchemeAtom(SchemeAtom::SchemeNull));
}
fn scheme_repr(ast: SchemeExpr) -> Result<String, &'static str> {
return Ok("It Worked!".to_string());
}
fn main() {
let stdin = io::stdin();
let mut stdout = io::stdout();
let raw_input = &mut String::new();
loop {
stdout.write(b"\nminimal-rust> ").unwrap();
stdout.flush().unwrap();
raw_input.clear();
stdin.read_line(raw_input).unwrap();
if raw_input.len() == 0 {
stdout.write(b"\nCiao!\n").unwrap();
return;
}
let tokens = scheme_tokenize(raw_input).unwrap();
let sexpr = scheme_parse_sexpr(tokens).unwrap();
let ast = scheme_parse(sexpr).unwrap();
let resp = scheme_eval(ast).unwrap();
println!("{}", scheme_repr(resp).unwrap());
}
}
|
