{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 5-5-4 Enumerator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[]"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = []"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: []:each>"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.each"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: []:each>"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[].each"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[]\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[]"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "p a \n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: []:each>"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[].each\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: {}:each>"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "{}.each"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "#<Enumerator: 1..10:each>\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "#<Enumerator: \"\":each_char>"
      ]
     },
     "execution_count": 28,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "p  (1..10).each\n",
    "''.each_char"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: 10:times>"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "10.times"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: main:loop>"
      ]
     },
     "execution_count": 30,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "loop"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "#<Enumerator: [1, 2, 3]:each>\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "#<Enumerator: \"Alice\":each_char>"
      ]
     },
     "execution_count": 31,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "p [1, 2, 3].to_enum\n",
    "'Alice'.enum_for(:each_char)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "#<Enumerator: \"Alice\\nBob\\nCharlie\\n\":each_line>\n",
      "[6, 4, 8]\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[6, 4, 8]"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "lines = <<EOM\n",
    "Alice\n",
    "Bob\n",
    "Charlie\n",
    "EOM\n",
    "\n",
    "p enum = lines.each_line\n",
    "p enum.map {|line| line.length}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: #<Enumerator: \"Alice\\nBob\\nCharlie\\n\":each_line>:map>"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "enum.map"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0: Alice\n",
      "1: Bob\n",
      "2: Charlie\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[\"Alice\", \"Bob\", \"Charlie\"]"
      ]
     },
     "execution_count": 35,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%w(Alice Bob Charlie).each.with_index do |n, i|\n",
    "    puts \"#{i}: #{n}\"\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[\"Luige\", \"Link\"]"
      ]
     },
     "execution_count": 37,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%w(Mario Luige Link).select.with_index {|n, i|\n",
    "  i > 0\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n",
      "4\n",
      "2\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 39,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "enum = [4, 4, 2, 3].to_enum\n",
    "\n",
    "p enum.next\n",
    "p enum.next\n",
    "p enum.next"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "4"
      ]
     },
     "execution_count": 40,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "enum.rewind\n",
    "\n",
    "enum.next"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n",
      "4\n",
      "2\n",
      "3\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[4, 4, 2, 3]"
      ]
     },
     "execution_count": 41,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "enum.rewind\n",
    "\n",
    "loop do\n",
    "  puts enum.next\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "A (14)\n",
      "B (32)\n",
      "C (28)\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[\"A\", \"B\", \"C\"]"
      ]
     },
     "execution_count": 43,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "people = %w(A B C).to_enum\n",
    "ages = [14, 32, 28].to_enum\n",
    "\n",
    "loop do \n",
    "  person = people.next\n",
    "  age    = ages.next\n",
    "  \n",
    "  puts \"#{person} (#{age})\"\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "A (14)\n",
      "B (32)\n",
      "C (28)\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "[[\"A\", 14], [\"B\", 32], [\"C\", 28]]"
      ]
     },
     "execution_count": 44,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "people.zip(ages).each do |p, a|\n",
    "  puts \"#{p} (#{a})\"\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "#<Enumerator: [[\"A\", 14], [\"B\", 32], [\"C\", 28]]:each>"
      ]
     },
     "execution_count": 46,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "people.zip(ages).to_enum"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 47,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "A (14)\n",
      "B (32)\n",
      "C (28)\n"
     ]
    }
   ],
   "source": [
    "people.zip(ages) do |p, a|\n",
    "  puts \"#{p} (#{a})\"\n",
    "end\n",
    "# メモリは食ってる？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[\"Alice\", \"Charlie\"]\n"
     ]
    }
   ],
   "source": [
    "enum = %w(Alice Bob Charlie).select\n",
    "\n",
    "loop do \n",
    "  begin\n",
    "    person = enum.next\n",
    "    \n",
    "    enum.feed /li/ === person\n",
    "  rescue StopIteration => e\n",
    "    p e.result\n",
    "    \n",
    "    break\n",
    "  end\n",
    "end\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[\"Bob\"]\n"
     ]
    }
   ],
   "source": [
    "enum = %w(Alice Bob Charlie).select\n",
    "\n",
    "loop do \n",
    "  begin\n",
    "    person = enum.next\n",
    "    \n",
    "    enum.feed person.size < 4\n",
    "  rescue StopIteration => e\n",
    "    p e.result\n",
    "    \n",
    "    break\n",
    "  end\n",
    "end"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "次回は \"5-5-5 Enumrator::Lazy\" から"
   ]
  }
 ],
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