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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
use crate::errors::{report, Error, ErrorKind};
use crate::parser::{self, Declaration, Expr, Literal, Program, Statement};
use crate::scanner::{self, TokenKind};
// Run some Lox code and print it to stdout
pub fn run(code: &str) {
let chars: Vec<char> = code.chars().collect();
match scanner::scan(&chars) {
Ok(tokens) => match parser::parse(tokens) {
Ok(program) => {
println!("Program:\n{:?}", program);
if let Err(err) = run_program(&program) {
println!("Error in program: {:?}", err);
}
}
Err(errors) => report_errors(errors),
},
Err(errors) => report_errors(errors),
}
}
fn report_errors(errors: Vec<Error>) {
for error in errors {
report(&error);
}
}
// Tree-walk interpreter
fn eval_truthy(lit: &Literal) -> bool {
match lit {
Literal::Nil => false,
Literal::Boolean(b) => *b,
_ => true,
}
}
fn eval_unary<'a>(expr: &parser::Unary<'a>) -> Result<Literal, Error> {
let right = eval(&*expr.right)?;
match (&expr.operator.kind, right) {
(TokenKind::Minus, Literal::Number(num)) => Ok(Literal::Number(-num)),
(TokenKind::Bang, right) => Ok(Literal::Boolean(!eval_truthy(&right))),
(op, right) => Err(Error {
line: expr.operator.line,
kind: ErrorKind::TypeError(format!(
"Operator '{:?}' can not be called with argument '{:?}'",
op, right
)),
}),
}
}
fn eval_binary<'a>(expr: &parser::Binary<'a>) -> Result<Literal, Error> {
let left = eval(&*expr.left)?;
let right = eval(&*expr.right)?;
let result = match (&expr.operator.kind, left, right) {
// Numeric
(TokenKind::Minus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l - r),
(TokenKind::Slash, Literal::Number(l), Literal::Number(r)) => Literal::Number(l / r),
(TokenKind::Star, Literal::Number(l), Literal::Number(r)) => Literal::Number(l * r),
(TokenKind::Plus, Literal::Number(l), Literal::Number(r)) => Literal::Number(l + r),
// Strings
(TokenKind::Plus, Literal::String(l), Literal::String(r)) => {
Literal::String(format!("{}{}", l, r))
}
// Comparators (on numbers only?)
(TokenKind::Greater, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l > r),
(TokenKind::GreaterEqual, Literal::Number(l), Literal::Number(r)) => {
Literal::Boolean(l >= r)
}
(TokenKind::Less, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l < r),
(TokenKind::LessEqual, Literal::Number(l), Literal::Number(r)) => Literal::Boolean(l <= r),
// Equality
(TokenKind::Equal, l, r) => Literal::Boolean(l == r),
(TokenKind::BangEqual, l, r) => Literal::Boolean(l != r),
(op, left, right) => {
return Err(Error {
line: expr.operator.line,
kind: ErrorKind::TypeError(format!(
"Operator '{:?}' can not be called with arguments '({:?}, {:?})'",
op, left, right
)),
})
}
};
Ok(result)
}
fn eval<'a>(expr: &Expr<'a>) -> Result<Literal, Error> {
match expr {
Expr::Literal(lit) => Ok(lit.clone()),
Expr::Grouping(grouping) => eval(&*grouping.0),
Expr::Unary(unary) => eval_unary(unary),
Expr::Binary(binary) => eval_binary(binary),
Expr::Variable(_) => unimplemented!(),
}
}
fn run_stmt<'a>(stmt: &Statement<'a>) -> Result<(), Error> {
match stmt {
Statement::Expr(expr) => {
eval(expr)?;
}
Statement::Print(expr) => {
let result = eval(expr)?;
println!("{:?}", result)
}
}
Ok(())
}
fn run_program<'a>(program: &Program<'a>) -> Result<(), Error> {
for decl in program {
match decl {
Declaration::Stmt(stmt) => run_stmt(stmt)?,
Declaration::Var(_var) => unimplemented!(),
}
}
Ok(())
}
|
