OldTerminal/Assets/Scripts/ProgrammerCalculator.cs

using System;
using System.Collections.Generic;
using System.Numerics;
using UnityEngine;

public class ProgrammerCalculator : MonoBehaviour
{
    public int CurrentBase { get; private set; } = 10;

    public void SetBase(int b)
    {
        CurrentBase = b;
    }

    // ===== PUBLIC API =====

    public string Evaluate(string expression)
    {
        var tokens = Tokenize(expression);
        print(tokens);
        foreach (var token in  tokens)
            print(token);
        var rpn = ToRPN(tokens);
        print(rpn);
        foreach (var rpnn in rpn)
            print(rpnn);
        BigInteger result = EvalRPN(rpn);
        print(result);
        return ToBaseString(result, CurrentBase);
    }

    // ===== TOKENIZER =====

    private List<string> Tokenize(string expr)
    {
        List<string> tokens = new List<string>();
        string num = "";

        foreach (char c in expr.ToUpper())
        {
            if (char.IsLetterOrDigit(c))
            {
                num += c;
            }
            else if ("+-*/()".Contains(c))
            {
                if (num != "")
                {
                    tokens.Add(num);
                    num = "";
                }
                tokens.Add(c.ToString());
            }
        }

        if (num != "")
            tokens.Add(num);

        return tokens;
    }

    // ===== SHUNTING YARD =====

    private int Precedence(string op)
    {
        return (op == "+" || op == "-") ? 1 :
               (op == "*" || op == "/") ? 2 : 0;
    }

    private List<string> ToRPN(List<string> tokens)
    {
        List<string> output = new List<string>();
        Stack<string> ops = new Stack<string>();

        foreach (var t in tokens)
        {
            if (IsNumber(t))
            {
                output.Add(t);
            }
            else if ("+-*/".Contains(t))
            {
                while (ops.Count > 0 && Precedence(ops.Peek()) >= Precedence(t))
                    output.Add(ops.Pop());
                ops.Push(t);
            }
            else if (t == "(")
            {
                ops.Push(t);
            }
            else if (t == ")")
            {
                while (ops.Peek() != "(")
                    output.Add(ops.Pop());
                ops.Pop();
            }
        }

        while (ops.Count > 0)
            output.Add(ops.Pop());

        return output;
    }

    // ===== RPN EVALUATION =====

    private BigInteger EvalRPN(List<string> rpn)
    {
        Stack<BigInteger> stack = new Stack<BigInteger>();

        foreach (var t in rpn)
        {
            if (IsNumber(t))
            {
                stack.Push(ParseNumber(t));
            }
            else
            {
                BigInteger b = stack.Pop();
                BigInteger a = stack.Pop();
                stack.Push(ApplyOp(a, b, t));
            }
        }

        return stack.Pop();
    }

    private BigInteger ApplyOp(BigInteger a, BigInteger b, string op)
    {
        return op switch
        {
            "+" => a + b,
            "-" => a - b,
            "*" => a * b,
            "/" => b == 0 ? 0 : a / b,
            _ => 0
        };
    }

    // ===== NUMBER UTILS =====

    private bool IsNumber(string s)
    {
        foreach (char c in s)
        {
            if (!char.IsDigit(c) && !(c >= 'A' && c <= 'F'))
                return false;
        }
        return true;
    }

    private BigInteger ParseNumber(string s)
    {
        switch (CurrentBase)
        {
            case 16:
                return BigInteger.Parse(s, System.Globalization.NumberStyles.HexNumber);
            case 10:
                return BigInteger.Parse(s);
            case 8:
                return ParseBase(s, 8);
            case 2:
                return ParseBase(s, 2);
            default:
                throw new Exception("Unsupported base");
        }
    }

    // <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD> base 2 <20> 8
    private BigInteger ParseBase(string s, int b)
    {
        BigInteger result = 0;
        foreach (char c in s)
        {
            int digit = c - '0';
            if (digit >= b) throw new Exception("Invalid digit for base " + b);
            result = result * b + digit;
        }
        return result;
    }



    private string ToBaseString(BigInteger val, int b)
    {
        if (b == 10) return val.ToString();
        if (val == 0) return "0";

        bool neg = val < 0;
        if (neg) val = BigInteger.Abs(val);

        string digits = "0123456789ABCDEF";
        string result = "";

        while (val > 0)
        {
            int d = (int)(val % b);
            result = digits[d] + result;
            val /= b;
        }

        return neg ? "-" + result : result;
    }
}