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
|
/*
* Minimal term re-writing system
*/
use crate::cexpr::{CExpr, CNumber};
use crate::sexpr::SExpr;
use crate::Result;
use std::collections::HashMap;
// for now these are hard coded
#[derive(Clone, PartialEq, Debug)]
pub enum RulePredicate {
IsNumber,
IsSymbol,
IsInteger,
IsEven,
IsOdd,
IsPositive,
IsNegative,
}
#[derive(Clone, PartialEq, Debug)]
pub enum CExprType {
Sum,
Product,
Factorial,
Exponential,
UnaryFunction(String),
}
#[derive(Clone, PartialEq, Debug)]
pub enum RuleExpr {
Var(char),
VarList(char),
Atom(CExpr),
List(CExprType, Vec<RuleExpr>),
}
#[derive(Clone, PartialEq, Debug)]
pub struct Rule {
variables: HashMap<char, Vec<RulePredicate>>,
pattern: RuleExpr,
substitute: RuleExpr,
}
impl RulePredicate {
pub fn from_sexpr(sexpr: &SExpr) -> Result<RulePredicate> {
use RulePredicate::*;
match sexpr {
SExpr::SIdentifier(v) => match v.as_str() {
"number?" => Ok(IsNumber),
"symbol?" => Ok(IsSymbol),
"integer?" => Ok(IsInteger),
"even?" => Ok(IsEven),
"odd?" => Ok(IsOdd),
"positive?" => Ok(IsPositive),
"negative?" => Ok(IsNegative),
_ => Err(format!("not a known predicate: {:?}", sexpr)),
},
_ => Err(format!("not a known predicate: {:?}", sexpr)),
}
}
pub fn check(self, cexpr: &CExpr) -> bool {
use CExpr::*;
use CNumber::*;
use RulePredicate::*;
match (self, cexpr) {
(IsNumber, Number(_)) => true,
(IsSymbol, Symbol(_)) => true,
(IsInteger, Number(Integer(_))) => true,
(IsEven, Number(Integer(n))) => n % 2 == 0,
(IsOdd, Number(Integer(n))) => n % 2 == 1,
(IsPositive, Number(Integer(n))) => n >= &0,
(IsNegative, Number(Integer(n))) => n < &0,
_ => false,
}
}
}
fn extract_vars(sexpr: &SExpr) -> Result<Option<HashMap<char, Vec<RulePredicate>>>> {
let slist = match sexpr {
SExpr::SList(l) => l,
_ => return Ok(None),
};
if matches!(slist.as_slice(), [SExpr::SIdentifier(head), SExpr::SIdentifier(var_name), ..] if head == "?" && var_name.len() == 1)
{
if let [SExpr::SIdentifier(_), SExpr::SIdentifier(var_name), pred_list @ ..] =
slist.as_slice()
{
let predicates: Vec<RulePredicate> = pred_list
.iter()
.map(|v| RulePredicate::from_sexpr(v))
.collect::<Result<Vec<RulePredicate>>>()?;
// TODO: why did HashMap::from([(c, predicates)]) not work here? rustc version?
let mut hm = HashMap::new();
hm.insert(var_name.chars().nth(0).unwrap(), predicates);
return Ok(Some(hm));
}
}
let sub_vars = slist.iter().filter_map(|v| extract_vars(v).unwrap()).fold(
HashMap::new(),
|mut acc, hm| {
acc.extend(hm);
acc
},
);
if sub_vars.is_empty() {
return Ok(None);
} else {
return Ok(Some(sub_vars));
}
}
impl RuleExpr {
pub fn from_sexpr(sexpr: &SExpr) -> Result<RuleExpr> {
// not all cases are handled; some atoms are covered trivialy
match sexpr {
SExpr::SNull | SExpr::SBoolean(_) | SExpr::SString(_) => {
Err("unhandled s-expr atoms; expected rule pattern".to_string())
}
SExpr::SInteger(_) | SExpr::SFloat(_) | SExpr::SIdentifier(_) => {
Ok(RuleExpr::Atom(CExpr::from_sexpr(sexpr)?))
}
SExpr::SList(list) => {
if let [SExpr::SIdentifier(ident), rest @ ..] = list.as_slice() {
match (ident.as_str(), rest.len()) {
("?", 1..=5000) => {
if let SExpr::SIdentifier(var_name) = &rest[0] {
Ok(RuleExpr::Var(var_name.chars().nth(0).unwrap()))
} else {
Err("expected single-character pattern name".to_string())
}
}
("?*", 1..=5000) => {
if let SExpr::SIdentifier(var_name) = &rest[0] {
Ok(RuleExpr::VarList(var_name.chars().nth(0).unwrap()))
} else {
Err("expected single-character pattern name".to_string())
}
}
("factorial", 1) => Ok(RuleExpr::List(
CExprType::Factorial,
rest.iter()
.map(|v| RuleExpr::from_sexpr(v))
.collect::<Result<Vec<RuleExpr>>>()?,
)),
("cos" | "sin" | "tan", 1) => Ok(RuleExpr::List(
CExprType::UnaryFunction(ident.to_string()),
rest.iter()
.map(|v| RuleExpr::from_sexpr(v))
.collect::<Result<Vec<RuleExpr>>>()?,
)),
("^", 2) => Ok(RuleExpr::List(
CExprType::Exponential,
rest.iter()
.map(|v| RuleExpr::from_sexpr(v))
.collect::<Result<Vec<RuleExpr>>>()?,
)),
("+", 2..=5000) => Ok(RuleExpr::List(
CExprType::Sum,
rest.iter()
.map(|v| RuleExpr::from_sexpr(v))
.collect::<Result<Vec<RuleExpr>>>()?,
)),
("*", 2..=5000) => Ok(RuleExpr::List(
CExprType::Product,
rest.iter()
.map(|v| RuleExpr::from_sexpr(v))
.collect::<Result<Vec<RuleExpr>>>()?,
)),
_ => Err("unhandled rule expression type".to_string()),
}
} else {
Err("unhandled rule expression type".to_string())
}
}
}
}
}
impl Rule {
pub fn from_sexpr(sexpr: &SExpr) -> Result<Rule> {
let slist = match sexpr {
SExpr::SList(l) => l,
_ => return Err("expected a rule".to_string()),
};
let (pattern, substitute) =
if let [SExpr::SIdentifier(name), pattern, substitute] = slist.as_slice() {
if name != "rule" {
return Err("expected a rule".to_string());
}
(pattern, substitute)
} else {
return Err("expected a rule".to_string());
};
// extract vars and predicates from pattern
let vars = match extract_vars(&pattern)? {
Some(hm) => hm,
None => HashMap::new(),
};
// parse pattern and substitute as RuleExpr
Ok(Rule {
variables: vars,
pattern: RuleExpr::from_sexpr(&pattern)?,
substitute: RuleExpr::from_sexpr(&substitute)?,
})
}
pub fn from_str(raw: &str) -> Result<Rule> {
let ast = SExpr::from_str(raw)?;
Rule::from_sexpr(&ast)
}
}
|
