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
|
use std::collections::HashMap;
#[derive(Debug, Copy, Clone, PartialEq)]
pub struct Operator {
token: char,
pub operation: fn(f64, f64) -> f64,
pub precedence: u8,
pub is_left_associative: bool,
}
impl Operator {
fn token_from_op(token: char, operation: fn(f64, f64) -> f64, precedence: u8, is_left_associative: bool) -> Token {
Token::Operator(
Operator {
token,
operation,
precedence,
is_left_associative
}
)
}
pub fn operate(self, x: f64, y: f64) -> f64 {
(self.operation)(x, y)
}
}
#[derive(Debug, Clone, PartialEq)]
pub struct Function {
token: String,
relation: fn(f64) -> f64,
}
impl Function {
fn token_from_fn(token: String, relation: fn(f64) -> f64) -> Token {
Token::Function(
Function {
token,
relation
}
)
}
pub fn apply(self, arg: f64) -> f64 {
(self.relation)(arg)
}
}
#[derive(Debug, Clone, PartialEq)]
pub enum Token {
Operator(Operator),
Num(f64),
Function(Function),
LParen,
RParen
}
fn get_functions() -> HashMap<&'static str, Token> {
return [
("sin", Function::token_from_fn("sin".into(), |x| x.to_radians().sin())),
("cos", Function::token_from_fn("cos".into(), |x| x.to_radians().cos())),
("tan", Function::token_from_fn("tan".into(), |x| x.to_radians().tan())),
("csc", Function::token_from_fn("csc".into(), |x| x.to_radians().sin().recip())),
("sec", Function::token_from_fn("sec".into(), |x| x.to_radians().cos().recip())),
("cot", Function::token_from_fn("cot".into(), |x| x.to_radians().tan().recip())),
("sinh", Function::token_from_fn("sinh".into(), |x| x.sinh())),
("cosh", Function::token_from_fn("cosh".into(), |x| x.cosh())),
("tanh", Function::token_from_fn("tanh".into(), |x| x.tanh())),
("ln", Function::token_from_fn("ln".into(), |x| x.ln())),
("log", Function::token_from_fn("log".into(), |x| x.log10())),
("sqrt", Function::token_from_fn("sqrt".into(), |x| x.sqrt())),
("ceil", Function::token_from_fn("ceil".into(), |x| x.ceil())),
("floor", Function::token_from_fn("floor".into(), |x| x.floor())),
// single arg functions can be added here
].iter().cloned().collect();
}
fn get_operators() -> HashMap<char, Token> {
return [
('+', Operator::token_from_op('+', |x, y| x + y, 2, true)),
('-', Operator::token_from_op('-', |x, y| x - y, 2, true)),
('*', Operator::token_from_op('*', |x, y| x * y, 3, true)),
('/', Operator::token_from_op('/', |x, y| x / y, 3, true)),
('^', Operator::token_from_op('^', |x, y| x.powf(y) , 4, false)),
].iter().cloned().collect();
}
pub fn lexer(input: &str) -> Result<Vec<Token>, String> {
let functions: HashMap<&str, Token> = get_functions();
let operators: HashMap<char, Token> = get_operators();
let mut num_vec: String = String::new();
let mut char_vec: String = String::new();
let mut result: Vec<Token> = vec![];
let mut last_char_is_op = true;
for letter in input.chars() {
match letter {
'0'...'9' | '.' => {
num_vec.push(letter);
last_char_is_op = false; // 5 - 6
// ^---- binary
},
'a'...'z' | 'A'...'Z' => {
let parse_num = num_vec.parse::<f64>().ok();
if let Some(x) = parse_num {
result.push(Token::Num(x));
result.push(operators.get(&'*').unwrap().clone());
num_vec.clear();
}
char_vec.push(letter);
last_char_is_op = false; // + or - can never be encountered right after a character
},
'+' | '-' => {
let op_token = operators.get(&letter).unwrap().clone();
let parse_num = num_vec.parse::<f64>().ok();
if !last_char_is_op {
if let Some(x) = parse_num {
result.push(Token::Num(x));
num_vec.clear();
last_char_is_op = true;
}
result.push(op_token);
} else if last_char_is_op { // act as unary only if an operator was parsed previously
result.push(Token::LParen);
result.push(Token::Num((letter.to_string() + "1").parse::<f64>().unwrap()));
result.push(Token::RParen);
result.push(Operator::token_from_op('*', |x, y| x * y, 10, true));
}
},
'/' | '*' | '^' => {
drain_num_stack(&mut num_vec, &mut result);
let operator_token: Token = operators.get(&letter).unwrap().clone();
result.push(operator_token);
last_char_is_op = true; // 5 / -5
// ^---- unary
// TODO: parse right associative followed by unary properly
// 2^+5 is parsed as 2^1*5 = 10
},
'(' => {
if char_vec.len() > 0 {
if let Some(res) = functions.get(&char_vec[..]) {
result.push(res.clone());
} else {
return Err(format!("Unexpected function {}", char_vec))
}
char_vec.clear();
} else {
let parse_num = num_vec.parse::<f64>().ok();
if let Some(x) = parse_num {
result.push(Token::Num(x));
result.push(operators.get(&'*').unwrap().clone());
num_vec.clear();
}
}
if let Some(x) = result.last() {
match x {
Token::RParen => {
result.push(operators.get(&'*').unwrap().clone());
},
_ => {}
};
}
result.push(Token::LParen);
last_char_is_op = true; // unary + or - if a lparen was encountered
// (-5 + 6) or (+6 + 7)
// ^ ^
// `-----------`----unary
},
')' => {
drain_num_stack(&mut num_vec, &mut result);
result.push(Token::RParen);
last_char_is_op = false; // binary + or - if rparen was encountered
// (1 + 2) - (3 + 4)
// ^ binary minus
}
' ' => {}
_ => {
return Err(format!("Unexpected character: {}", letter))
}
}
}
drain_num_stack(&mut num_vec, &mut result);
Ok(result)
}
fn drain_num_stack(num_vec: &mut String, result: &mut Vec<Token>) {
let parse_num = num_vec.parse::<f64>().ok();
if let Some(x) = parse_num {
result.push(Token::Num(x));
num_vec.clear();
}
}
|
