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
|
use std::f64;
mod lex;
use crate::lex::*;
mod parse;
use crate::parse::*;
mod error;
use crate::error::{ CalcError, handler };
use rustyline::error::ReadlineError;
use rustyline::Editor;
use rustyline::config::{ Config, Builder, ColorMode, EditMode };
fn main() {
let config_builder = Builder::new();
let config = config_builder.color_mode(ColorMode::Enabled)
.edit_mode(EditMode::Emacs)
.history_ignore_space(true)
.max_history_size(1000)
.build();
let mut rl = Editor::<()>::with_config(config);
if rl.load_history("history.txt").is_err() {
println!("No previous history.");
}
loop {
let readline = rl.readline("> ");
match readline {
Ok(line) => {
rl.add_history_entry(line.as_ref());
let evaled = eval_math_expression(&line[..]);
match evaled {
Ok(ans) => println!("{}", ans),
Err(e) => handler(e),
};
},
Err(ReadlineError::Interrupted) => {
println!("CTRL-C");
break
},
Err(ReadlineError::Eof) => {
println!("CTRL-D");
break
},
Err(err) => {
println!("Error: {:?}", err);
break
}
}
}
rl.save_history("history.txt").unwrap();
}
fn autobalance_parens(input: &str) -> Result<String, CalcError> {
let mut balanced = String::from(input);
let mut left_parens = 0;
let mut right_parens = 0;
for letter in input.chars() {
if letter == '(' {
left_parens += 1;
} else if letter == ')' {
right_parens += 1;
}
}
if left_parens > right_parens {
let extras = ")".repeat(left_parens - right_parens);
balanced.push_str(&extras[..]);
Ok(balanced)
} else if left_parens < right_parens {
return Err(CalcError::Syntax("Mismatched parentheses!".into()))
} else {
Ok(balanced)
}
}
fn eval_math_expression(input: &str) -> Result<f64, CalcError> {
let input = autobalance_parens(&input[..])?;
let lexed = lexer(&input[..])?;
let postfixed = to_postfix(lexed)?;
let evaled = eval_postfix(postfixed)?;
Ok(evaled)
}
|
