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use std::io::{ stdin };
use std::f64;
mod lex;
use crate::lex::*;
mod parse;
use crate::parse::*;
fn main() {
loop {
let mut input = String::new();
stdin().read_line(&mut input).unwrap();
let input = input.trim();
let input = input.replace(" ", "");
if input == "exit" {
return
}
println!("ans: {}\n", eval_math_expression(&input[..]).unwrap());
}
}
fn autobalance_parens(input: &str) -> Result<String, String> {
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(format!("Mismatched parentheses"))
} else {
Ok(balanced)
}
}
fn eval_math_expression(input: &str) -> Result<f64, String> {
let input = autobalance_parens(&input[..])?;
let lexed = lexer(&input[..])?;
let postfixed = to_postfix(lexed)?;
let evaled = eval_postfix(postfixed)?;
Ok(evaled)
}
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