euler46.ipynb

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   4    "cell_type": "code",
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   8    },
   9    "outputs": [
  10     {
  11      "data": {
  12       "text/plain": [
  13        "true"
  14       ]
  15      },
  16      "execution_count": 1,
  17      "metadata": {},
  18      "output_type": "execute_result"
  19     }
  20    ],
  21    "source": [
  22     "load 'primes.rb'"
  23    ]
  24   },
  25   {
  26    "cell_type": "code",
  27    "execution_count": 7,
  28    "metadata": {
  29     "collapsed": false
  30    },
  31    "outputs": [
  32     {
  33      "data": {
  34       "text/plain": [
  35        ":gb_test_one"
  36       ]
  37      },
  38      "execution_count": 7,
  39      "metadata": {},
  40      "output_type": "execute_result"
  41     }
  42    ],
  43    "source": [
  44     "def gb_test_one(n, s)\n",
  45     "  p = n - 2 * s ** 2\n",
  46     "  p.prime?\n",
  47     "end"
  48    ]
  49   },
  50   {
  51    "cell_type": "code",
  52    "execution_count": 10,
  53    "metadata": {
  54     "collapsed": false
  55    },
  56    "outputs": [
  57     {
  58      "data": {
  59       "text/plain": [
  60        ":other_goldbach"
  61       ]
  62      },
  63      "execution_count": 10,
  64      "metadata": {},
  65      "output_type": "execute_result"
  66     }
  67    ],
  68    "source": [
  69     "def other_goldbach(n)\n",
  70     "  s_limit = Math.sqrt(n / 2).floor\n",
  71     "  (1..s_limit).any? {|s| gb_test_one n, s}\n",
  72     "end"
  73    ]
  74   },
  75   {
  76    "cell_type": "code",
  77    "execution_count": 11,
  78    "metadata": {
  79     "collapsed": false
  80    },
  81    "outputs": [
  82     {
  83      "data": {
  84       "text/plain": [
  85        "true"
  86       ]
  87      },
  88      "execution_count": 11,
  89      "metadata": {},
  90      "output_type": "execute_result"
  91     }
  92    ],
  93    "source": [
  94     "other_goldbach(9)"
  95    ]
  96   },
  97   {
  98    "cell_type": "code",
  99    "execution_count": 28,
 100    "metadata": {
 101     "collapsed": false
 102    },
 103    "outputs": [
 104     {
 105      "data": {
 106       "text/plain": [
 107        ":sequence"
 108       ]
 109      },
 110      "execution_count": 28,
 111      "metadata": {},
 112      "output_type": "execute_result"
 113     }
 114    ],
 115    "source": [
 116     "def sequence(&generator)\n",
 117     "  Enumerator.new do |yielder|\n",
 118     "    n = 0\n",
 119     "    loop do\n",
 120     "      yielder.yield generator.call(n)\n",
 121     "      n = n + 1\n",
 122     "    end\n",
 123     "  end\n",
 124     "end"
 125    ]
 126   },
 127   {
 128    "cell_type": "code",
 129    "execution_count": 40,
 130    "metadata": {
 131     "collapsed": false
 132    },
 133    "outputs": [
 134     {
 135      "data": {
 136       "text/plain": [
 137        "#<Enumerator::Lazy: #<Enumerator::Lazy: #<Enumerator::Lazy: #<Enumerator: #<Enumerator::Generator:0x00557af0bf6f10>:each>>:drop(1)>:select>"
 138       ]
 139      },
 140      "execution_count": 40,
 141      "metadata": {},
 142      "output_type": "execute_result"
 143     }
 144    ],
 145    "source": [
 146     "odds = sequence {|i| 2 * i + 1}\n",
 147     "candidates = odds.lazy.drop(1).select {|i| !i.prime?}"
 148    ]
 149   },
 150   {
 151    "cell_type": "code",
 152    "execution_count": 41,
 153    "metadata": {
 154     "collapsed": false
 155    },
 156    "outputs": [
 157     {
 158      "data": {
 159       "text/plain": [
 160        "[9, 15, 21, 25, 27, 33, 35, 39, 45, 49]"
 161       ]
 162      },
 163      "execution_count": 41,
 164      "metadata": {},
 165      "output_type": "execute_result"
 166     }
 167    ],
 168    "source": [
 169     "candidates.take(10).force"
 170    ]
 171   },
 172   {
 173    "cell_type": "code",
 174    "execution_count": 44,
 175    "metadata": {
 176     "collapsed": false
 177    },
 178    "outputs": [
 179     {
 180      "data": {
 181       "text/plain": [
 182        "[5777]"
 183       ]
 184      },
 185      "execution_count": 44,
 186      "metadata": {},
 187      "output_type": "execute_result"
 188     }
 189    ],
 190    "source": [
 191     "candidates.reject {|i| other_goldbach i}.take(1).force"
 192    ]
 193   },
 194   {
 195    "cell_type": "code",
 196    "execution_count": null,
 197    "metadata": {
 198     "collapsed": true
 199    },
 200    "outputs": [],
 201    "source": []
 202   }
 203  ],
 204  "metadata": {
 205   "kernelspec": {
 206    "display_name": "Ruby 2.4.0",
 207    "language": "ruby",
 208    "name": "ruby"
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 210   "language_info": {
 211    "file_extension": ".rb",
 212    "mimetype": "application/x-ruby",
 213    "name": "ruby",
 214    "version": "2.4.0"
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 219 }