python_and_fp.ipynb

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   "source": [
    "# Python come Linguaggio Funzionale"
   ]
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   "source": [
    "## Python è un linguaggio funzionale?\n",
    "### No"
   ]
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   "source": [
    "Caratteristiche di un linguaggio funzionale:\n",
    "\n",
    "- Le funzioni sono first class object\n",
    "- Ricorsione come struttura di controllo\n",
    "- Non sono permessi effetti collaterali -> (oggetti immutabili)\n",
    "- Cosa vs Come\n",
    "- Higher order functions -> funzioni che usano funzioni"
   ]
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   "source": [
    "Ma non ci sono ottimizzazioni tipiche della programmazione funzionale e c'è un `recursion limit`."
   ]
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    {
     "ename": "RecursionError",
     "evalue": "maximum recursion depth exceeded in comparison",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mRecursionError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-2-0bb760115389>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      5\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m*\u001b[0m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m1000\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;32m<ipython-input-2-0bb760115389>\u001b[0m in \u001b[0;36mfact_r\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      3\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 5\u001b[0;31m         \u001b[0;32mreturn\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m*\u001b[0m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      6\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      7\u001b[0m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m1000\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "... last 1 frames repeated, from the frame below ...\n",
      "\u001b[0;32m<ipython-input-2-0bb760115389>\u001b[0m in \u001b[0;36mfact_r\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      3\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 5\u001b[0;31m         \u001b[0;32mreturn\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m*\u001b[0m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      6\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      7\u001b[0m \u001b[0mfact_r\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m1000\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded in comparison"
     ]
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   "source": [
    "def fact_r(n):\n",
    "    if n == 1:\n",
    "        return 1\n",
    "    else:\n",
    "        return n * fact_r(n - 1)\n",
    "    \n",
    "fact_r(1000)"
   ]
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   "source": [
    "fact_r(100)"
   ]
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   "source": [
    "In realtà esistono altri modi per evitare il `RecursionError`"
   ]
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   "cell_type": "code",
   "execution_count": 16,
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     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "from operator import mul\n",
    "from functools import reduce\n",
    "\n",
    "\n",
    "def fact_nr(n):\n",
    "    return reduce(mul, range(1, n))\n",
    "\n",
    "fact_nr(1000)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "100000 loops, best of 3: 12.9 µs per loop\n"
     ]
    }
   ],
   "source": [
    "%timeit fact_r(100)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "100000 loops, best of 3: 7.2 µs per loop\n"
     ]
    }
   ],
   "source": [
    "%timeit fact_nr(100)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "Il recursion limit può essere anche cambiato:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true,
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   "outputs": [],
   "source": [
    "imp"
   ]
  }
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