main3.rs

use nom::{branch, bytes::complete::tag, character::complete::digit1, error, Err};
use nom_locate::LocatedSpan;

const INPUT: &str = "-2+3**2*3/5-4";
//const INPUT: &str = "2+-3";
//const INPUT: &str = "2+30000000000000000000000";
//const INPUT: &str = "2";
//const INPUT: &str = "30000000000000000000000";
//const INPUT: &str = "3+2a";

const UNARYS: [Funcmap; 1] = [Funcmap {
    keyword: "-",
    prec: 4,
    ass: Ass::Right,
    func: Function::UnSub,
}];

const INFIXS: [Funcmap; 5] = [
    Funcmap {
        keyword: "**",
        prec: 3,
        ass: Ass::Right,
        func: Function::Pow,
    },
    Funcmap {
        keyword: "*",
        prec: 2,
        ass: Ass::Left,
        func: Function::Mult,
    },
    Funcmap {
        keyword: "/",
        prec: 2,
        ass: Ass::Left,
        func: Function::Div,
    },
    Funcmap {
        keyword: "+",
        prec: 1,
        ass: Ass::Left,
        func: Function::Add,
    },
    Funcmap {
        keyword: "-",
        prec: 1,
        ass: Ass::Left,
        func: Function::Sub,
    },
];

struct Expr<'a> {
    span: Span<'a>,
    val: Value<'a>,
}

enum Value<'a> {
    Int(i32),
    UnFunc(Function, Box<Expr<'a>>),
    Func(Function, Box<Expr<'a>>, Box<Expr<'a>>),
}

#[derive(Clone, Copy)]
enum Function {
    UnSub,
    Pow,
    Mult,
    Div,
    Add,
    Sub,
}