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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| 1. / x.to_radians().sin())),
("sec", Function::token_from_fn("sec".into(), |x| 1. / x.to_radians().cos())),
("cot", Function::token_from_fn("cot".into(), |x| 1. / x.to_radians().tan())),
("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())),
].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, true)),
].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![];
for letter in input.chars() {
match letter {
'0'...'9' | '.' => {
num_vec.push(letter);
},
'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);
},
'+' | '-' => {
let op_token = operators.get(&letter).unwrap().clone();
let parse_num = num_vec.parse::<f64>().ok();
if let Some(x) = parse_num {
result.push(Token::Num(x));
num_vec.clear();
result.push(op_token);
} else {
result.push(Token::LParen);
result.push(Token::Num((letter.to_string() + "1").parse::<f64>().unwrap()));
result.push(Token::RParen);
result.push(operators.get(&'*').unwrap().clone());
}
},
'/' | '*' | '^' => {
drain_num_stack(&mut num_vec, &mut result);
let operator_token: Token = operators.get(&letter).unwrap().clone();
result.push(operator_token);
},
'(' => {
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);
},
')' => {
drain_num_stack(&mut num_vec, &mut result);
result.push(Token::RParen);
}
' ' => {}
_ => {
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();
}
}
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