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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
use crate::{
app::AppState,
lisp::{
error::{EvalError, LispError},
expr::{Arity, Ident, LispExpr, LispFunction},
number::LispNumber,
EnvList, Environment,
},
};
use std::convert::TryInto;
use log::{error, info};
pub fn eval(expr: &LispExpr, app: &mut AppState) -> Result<LispExpr, LispError> {
match expr {
LispExpr::Unit => Ok(expr.clone()),
LispExpr::StringLit(_) => Ok(expr.clone()),
LispExpr::Char(_) => Ok(expr.clone()),
LispExpr::Number(_) => Ok(expr.clone()),
LispExpr::BoolLit(_) => Ok(expr.clone()),
LispExpr::Ident(ref id) => lookup_extended(&app.lisp_env, id),
LispExpr::List(li) => {
let func_expr = &li[0];
match func_expr {
LispExpr::Ident(s) => match s.as_ref() {
"define" => define_var(&li[1..], app),
"set!" => set_var(&li[1..], app),
"lambda" => create_lambda(&li[1..]),
"if" => eval_if(&li[1..], app),
_ => {
let func_expr = eval(&func_expr, app)?;
match func_expr {
LispExpr::PrimitiveFunc(f) => {
let mut args = Vec::new();
for item in li[1..].iter() {
args.push(eval(item, app)?);
}
f.call(&args, app)
}
LispExpr::Function(f) => {
let mut args = Vec::new();
for item in li[1..].iter() {
let i = eval(item, app)?;
args.push(i);
}
if f.params.len() != args.len() {
info!("too many or too little number of args");
Err(EvalError::ArgumentCount(Arity::Exact(f.params.len()))
.into())
} else {
let nested_env: Environment =
f.params.into_iter().zip(args).collect();
app.lisp_env.push(nested_env);
let result = if f.body.is_empty() {
Ok(LispExpr::Unit)
} else {
eval(&LispExpr::List(f.body), app)
};
app.lisp_env.pop();
return result;
}
}
_ => Err(EvalError::BadForm.into()),
}
}
},
_ => Err(EvalError::BadForm.into()),
}
}
_ => Err(EvalError::BadForm.into()),
}
}
pub fn define_var(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(2);
if !arity.is_valid(args) {
return Err(arity.to_error());
}
match args {
[LispExpr::Ident(id), expr] => {
let value = eval(&expr, app)?;
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
env.insert(id.into(), value);
} else {
error!("Unable to create global definition");
return Err(EvalError::BadForm.into());
}
return Ok(LispExpr::Unit);
}
[LispExpr::List(shorthand), LispExpr::List(body)] => {
// (define (func arg) <body>) shorthand
let id = unwrap_ident(shorthand[0].clone());
let params = if shorthand.len() > 1 {
&shorthand[1..]
} else {
&[]
}
.to_vec()
.into_iter()
.map(|arg| arg.try_into())
.collect::<Result<Vec<Ident>, LispError>>()?;
let value = LispExpr::Function(LispFunction {
params,
body: body.to_vec(),
});
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
info!("creating function {}", id);
env.insert(id.into(), value);
} else {
error!("Unable to create global definition");
return Err(EvalError::BadForm.into());
}
return Ok(LispExpr::Unit);
}
_ => {
error!("Invalid usage of `define`");
Err(EvalError::BadForm.into())
}
}
}
pub fn set_var(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(2);
if !arity.is_valid(args) {
return Err(arity.to_error());
}
match args {
[LispExpr::Ident(id), expr] => {
let value = eval(&expr, app)?;
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
return env
.insert(id.into(), value)
.ok_or(EvalError::UnboundVariable(id.into()).into());
} else {
error!("Unable to set in global env!");
return Err(EvalError::BadForm.into());
}
}
_ => {
error!("Invalid usage of `set!`");
return Err(EvalError::BadForm.into());
}
}
}
pub fn create_lambda(cdr: &[LispExpr]) -> Result<LispExpr, LispError> {
let arity: Arity = Arity::Exact(2);
if !arity.is_valid(cdr) {
return Err(arity.to_error());
}
info!("creating lambda");
match cdr {
[LispExpr::List(params), LispExpr::List(body)]
if params.iter().all(|p| matches!(p, LispExpr::Ident(_))) =>
{
return Ok(LispExpr::Function(LispFunction {
params: params
.into_iter()
.map(|p| unwrap_ident(p.clone()))
.collect::<Vec<_>>(),
body: body.clone(),
}));
}
_ => {
error!("Invalid usage of `lambda`");
return Err(EvalError::BadForm.into());
}
}
}
pub fn eval_if(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(3);
if !arity.is_valid(args) {
return Err(arity.to_error());
} else {
match args {
[predicate, then, else_] => {
let predicate = eval(&predicate, app)?;
if matches!(predicate, LispExpr::BoolLit(false)) {
return eval(&else_, app);
} else {
return eval(&then, app);
}
}
_ => {
panic!("panicked at `if` expression")
}
}
}
}
pub fn lookup_extended(env_list: &[Environment], key: &str) -> Result<LispExpr, LispError> {
if env_list.is_empty() {
return Err(EvalError::UnboundVariable(key.into()).into());
} else {
let local_env = env_list.last().unwrap();
if let Some(val) = local_env.get(key) {
return Ok(val.clone());
} else {
return lookup_extended(&env_list[..env_list.len() - 1], key);
}
}
}
pub fn unwrap_number(n: &LispExpr) -> &LispNumber {
match n {
LispExpr::Number(i) => i,
_ => panic!("unwrap_number expected number"),
}
}
pub fn unwrap_ident(i: LispExpr) -> String {
match i {
LispExpr::Ident(i) => i,
_ => panic!("unwrap_ident expected string"),
}
}
|
