{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 48,
   "metadata": {},
   "outputs": [],
   "source": [
    "import re\n",
    "from decimal import Decimal\n",
    "from functools import reduce"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [],
   "source": [
    "def add(string):\n",
    "    while(len(re.findall(\"[+]{1}[-]?\", string)) != 0):\n",
    "        string = re.sub(\"[-]?\\d+[.]?\\d*[+]{1}[-]?\\d+[.]?\\d*\", str(sum([Decimal(i) for i in re.split(\"[+]{1}\", re.search(\"[-]?\\d+[.]?\\d*[+]{1}[-]?\\d+[.]?\\d*\", string).group())])), string, 1)\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {},
   "outputs": [],
   "source": [
    "def sub(string):\n",
    "    while(len(re.findall(\"\\d+[.]?\\d*[-]{1,2}\\d+[.]?\\d*\", string)) != 0):\n",
    "        g = re.search(\"\\d+[.]?\\d*[-]{1,2}\\d+[.]?\\d*\", string).group()\n",
    "        if(re.search(\"[-]{1,2}\", g).group() == \"-\"):\n",
    "            r = re.sub(\"[-]{1}\", \"+-\", g, 1)\n",
    "            string = re.sub(g, r, string, 1)\n",
    "        elif(re.search(\"[-]{1,2}\", g).group() == \"--\"):\n",
    "            r = re.sub(\"[-]{2}\", \"+\", g, 1)\n",
    "            string = re.sub(g, r, string, 1)\n",
    "        else:\n",
    "            pass\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 51,
   "metadata": {},
   "outputs": [],
   "source": [
    "def mul(string):\n",
    "    while(len(re.findall(\"[*]{1}[-]?\", string)) != 0):\n",
    "        string = re.sub(\"[-]?\\d+[.]?\\d*[*]{1}[-]?\\d+[.]?\\d*\", str(reduce((lambda x, y: x * y), [Decimal(i) for i in re.split(\"[*]{1}\", re.search(\"[-]?\\d+[.]?\\d*[*]{1}[-]?\\d+[.]?\\d*\", string).group())])), string, 1)\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [],
   "source": [
    "def div(string):\n",
    "    while(len(re.findall(\"[/]{1}[-]?\", string)) != 0):\n",
    "        string = re.sub(\"[-]?\\d+[.]?\\d*[/]{1}[-]?\\d+[.]?\\d*\", str(reduce((lambda x, y: x / y), [Decimal(i) for i in re.split(\"[/]{1}\", re.search(\"[-]?\\d+[.]?\\d*[/]{1}[-]?\\d+[.]?\\d*\", string).group())])), string, 1)\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [],
   "source": [
    "def exp(string):\n",
    "    while(len(re.findall(\"[\\^]{1}[-]?\", string)) != 0):\n",
    "        string = re.sub(\"[-]?\\d+[.]?\\d*[\\^]{1}[-]?\\d+[.]?\\d*\", str(reduce((lambda x, y: x ** y), [Decimal(i) for i in re.split(\"[\\^]{1}\", re.search(\"[-]?\\d+[.]?\\d*[\\^]{1}[-]?\\d+[.]?\\d*\", string).group())])), string, 1)\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 68,
   "metadata": {},
   "outputs": [],
   "source": [
    "def evaluate(string):\n",
    "    string = exp(string)\n",
    "    string = div(string)\n",
    "    string = mul(string)\n",
    "    string = sub(string)\n",
    "    string = add(string)\n",
    "    return string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 70,
   "metadata": {},
   "outputs": [
    {
     "output_type": "stream",
     "name": "stdout",
     "text": "-128+0.8\n"
    },
    {
     "output_type": "execute_result",
     "data": {
      "text/plain": "'-127.2'"
     },
     "metadata": {},
     "execution_count": 70
    }
   ],
   "source": [
    "string = \"8^2*4/-2+0.8\"\n",
    "evaluate(string)"
   ]
  }
 ],
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