languagedesign.ipynb

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    {
     "ename": "NameError",
     "evalue": "global name 'literal_token' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-2-1fca9150cc5b>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m     19\u001b[0m     \u001b[1;32mreturn\u001b[0m \u001b[0mexpression\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m     20\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m---> 21\u001b[1;33m \u001b[0mparse\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m\"1+2\"\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;32m<ipython-input-2-1fca9150cc5b>\u001b[0m in \u001b[0;36mparse\u001b[1;34m(program)\u001b[0m\n\u001b[0;32m     16\u001b[0m     \u001b[1;32mglobal\u001b[0m \u001b[0mtoken\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mnext\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m     17\u001b[0m     \u001b[0mnext\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mtokenize\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mprogram\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mnext\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m---> 18\u001b[1;33m     \u001b[0mtoken\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mnext\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m     19\u001b[0m     \u001b[1;32mreturn\u001b[0m \u001b[0mexpression\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m     20\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n",
      "\u001b[1;32m<ipython-input-2-1fca9150cc5b>\u001b[0m in \u001b[0;36mtokenize\u001b[1;34m(program)\u001b[0m\n\u001b[0;32m      6\u001b[0m     \u001b[1;32mfor\u001b[0m \u001b[0mnumber\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0moperator\u001b[0m \u001b[1;32min\u001b[0m \u001b[0mtoken_pat\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mfindall\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mprogram\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      7\u001b[0m         \u001b[1;32mif\u001b[0m \u001b[0mnumber\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 8\u001b[1;33m             \u001b[1;32myield\u001b[0m \u001b[0mliteral_token\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnumber\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m      9\u001b[0m         \u001b[1;32melif\u001b[0m \u001b[0moperator\u001b[0m \u001b[1;33m==\u001b[0m \u001b[1;34m\"+\"\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m     10\u001b[0m             \u001b[1;32myield\u001b[0m \u001b[0moperator_add_token\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
      "\u001b[1;31mNameError\u001b[0m: global name 'literal_token' is not defined"
     ]
    }
   ],
   "source": [
    "import re\n",
    "\n",
    "token_pat = re.compile(\"\\s*(?:(\\d+)|(.))\")\n",
    "\n",
    "def tokenize(program):\n",
    "    for number, operator in token_pat.findall(program):\n",
    "        if number:\n",
    "            yield literal_token(number)\n",
    "        elif operator == \"+\":\n",
    "            yield operator_add_token()\n",
    "        else:\n",
    "            raise SyntaxError(\"unknown operator\")\n",
    "    yield end_token()\n",
    "\n",
    "def parse(program):\n",
    "    global token, next\n",
    "    next = tokenize(program).next\n",
    "    token = next()\n",
    "    return expression()\n",
    "\n",
    "parse(\"1+2\")"
   ]
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