03a-solution_intro.ipynb

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     "cell_type": "code",
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     "input": [
      "# should return 3rd letter of text\n",
      "# in argument, if doesn't exists return `nil`\n",
      "def third_elem(thing)\n",
      "  if thing.length < 3\n",
      "    nil\n",
      "  else\n",
      "    thing[2]\n",
      "  end\n",
      "end\n",
      "# O'rly?"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "thing = \"oi\"\n",
      "thing[2]"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "subslide"
      }
     },
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr = ['sugar', 'spice']\n",
      "arr[2]"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "subslide"
      }
     },
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Do The Simplest Thing That Could Possibly Work"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def reverse_arg(thing)\n",
      "  thing = thing.class == String ? thing.to_s.reverse : thing.to_a.reverse\n",
      "end "
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [],
     "prompt_number": 6
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def reverse_arg(thing)\n",
      "  thing.reverse\n",
      "end "
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [],
     "prompt_number": 7
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    {
     "cell_type": "code",
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     "input": [
      "def reverse_arg(thing)\n",
      "  if thing.respond_to? :reverse\n",
      "    thing.reverse\n",
      "  else\n",
      "    throw ArgumentError.new(\"Gimme something reversable!\")\n",
      "  end\n",
      "end\n",
      "reverse_arg({})"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "subslide"
      }
     },
     "outputs": [
      {
       "ename": "ArgumentError",
       "evalue": "uncaught throw #<ArgumentError: Gimme something reversable!>",
       "output_type": "pyerr",
       "traceback": [
        "\u001b[31mArgumentError\u001b[0m: uncaught throw #<ArgumentError: Gimme something reversable!>",
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     "prompt_number": 9
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Constructors"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr = Array.new\n",
      "hsh = Hash.new\n",
      "\n",
      "p arr, hsh"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "[]"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{}"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 1,
       "text": [
        "[[], {}]"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr = []\n",
      "hsh = {}\n",
      "\n",
      "p arr, hsh"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "[]"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{}"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 2,
       "text": [
        "[[], {}]"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "hsh = {}\n",
      "p hsh[:a]"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "nil"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "hsh = Hash.new(0)\n",
      "p hsh[:a]"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "0"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "-"
      }
     },
     "source": [
      "http://ruby-doc.org/core-2.0.0/Hash.html#method-c-new"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Odd? Even?"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Not Ruby enough\n",
      "index = 1\n",
      "index % 2"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "-"
      }
     },
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 5,
       "text": [
        "1"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Better\n",
      "index = 1\n",
      "index.odd?"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "-"
      }
     },
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 6,
       "text": [
        "true"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Increment"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#i = nil\n",
      "i ||= 0\n",
      "i += 1"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "subslide"
      }
     },
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 7,
       "text": [
        "1"
       ]
      }
     ],
     "prompt_number": 7
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "String Replacement: `sub`, `gsub`"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "word = \"!Hello? ^_^\"\n",
      "# Worst\n",
      "word = word.sub '!', ''\n",
      "word = word.sub '?', ''\n",
      "word = word.sub '^', ''\n",
      "word = word.sub '_', ''"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 8,
       "text": [
        "Hello ^"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "word = \"!Hello? ^_^\"\n",
      "# Still pretty bad\n",
      "word.sub! '!', ''\n",
      "word.sub! '?', ''\n",
      "word.sub! '^', ''\n",
      "word.sub! '_', ''"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 9,
       "text": [
        "Hello ^"
       ]
      }
     ],
     "prompt_number": 9
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "word = \"!Hello? ^_^\"\n",
      "# Better\n",
      "word.gsub /[!\\?\\^_]/, ''"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 10,
       "text": [
        "Hello "
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "word = \"!Hello? ^_^\"\n",
      "# Smart\n",
      "word.gsub /[^a-zA-Z ]/, ''"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 11,
       "text": [
        "Hello "
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "word = \"!Hello? ^_^\"\n",
      "# Effin' smart\n",
      "word.gsub /[\\W_ ]/, ''"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 12,
       "text": [
        "Hello"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "If / Then"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "i_had_a_tail = true\n",
      "if(i_had_a_tail) then\n",
      "  \"I'd own the night\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 13,
       "text": [
        "I'd own the night"
       ]
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "> Never use then for multi-line `if`/`unless`.\n",
      ">\n",
      "> \u2014 [Ruby Style Guide](https://github.com/bbatsov/ruby-style-guide#syntax)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "if(i_had_a_tail) then \"I'd own the night\" end # Okay"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "I'd own the night"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Better\n",
      "if i_had_a_tail\n",
      "  \"I'd swat the flies\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 15,
       "text": [
        "I'd swat the flies"
       ]
      }
     ],
     "prompt_number": 15
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {},
     "source": [
      "Unless"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "if !i_had_a_tail\n",
      "  \"I'd swat the flies\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [],
     "prompt_number": 16
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "unless i_had_a_tail\n",
      "  \"I'd swat the flies\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [],
     "prompt_number": 17
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Each / For"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr = ['nothing', 'beer', 'wine', 'cider']\n",
      "for i in 0..(arr.length-1)\n",
      "  puts \"#{i} bottles of #{arr[i]}\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0 bottles of nothing\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 bottles of beer\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "2 bottles of wine\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3 bottles of cider\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 18,
       "text": [
        "0..3"
       ]
      }
     ],
     "prompt_number": 18
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "for i in 0...arr.length\n",
      "  puts \"#{i} bottles of #{arr[i]}\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0 bottles of nothing\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 bottles of beer\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "2 bottles of wine\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3 bottles of cider\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 19,
       "text": [
        "0...4"
       ]
      }
     ],
     "prompt_number": 19
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "> Never use `for`, unless you know exactly why. Most of the time iterators should be used instead. \n",
      ">\n",
      "> \u2014 [Ruby Style Guide](https://github.com/bbatsov/ruby-style-guide#syntax)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr.each_with_index do |container, count|\n",
      "  puts \"#{count} bottles of #{container}\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0 bottles of nothing\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 bottles of beer\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "2 bottles of wine\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3 bottles of cider\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 20,
       "text": [
        "[\"nothing\", \"beer\", \"wine\", \"cider\"]"
       ]
      }
     ],
     "prompt_number": 20
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "arr = ['nothing', 'beer', 'wine', 'cider']\n",
      "arr.each_with_index do |container, count|\n",
      "  next if count.even?\n",
      "  puts \"#{count} bottles of #{container}\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 bottles of beer\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3 bottles of cider\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 21,
       "text": [
        "[\"nothing\", \"beer\", \"wine\", \"cider\"]"
       ]
      }
     ],
     "prompt_number": 21
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Style"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "[Use the Guide!](https://github.com/bbatsov/ruby-style-guide)"
     ]
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {},
     "source": [
      "snake_case for variables and methods"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "myArray = [] # meh.\n",
      "my_array = [] # yay!"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 22,
       "text": [
        "[]"
       ]
      }
     ],
     "prompt_number": 22
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {},
     "source": [
      "Blocks"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "> Prefer `{...}` over `do...end` for **single-line blocks**.<br>\n",
      "> Avoid using `{...}` for **multi-line blocks** (multiline chaining is always ugly).\n",
      ">\n",
      "> \u2014 [Ruby Style Guide](https://github.com/bbatsov/ruby-style-guide#syntax)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Ugly!\n",
      "File.open(\"testfile\",\"w\") { |file|\n",
      "  file << \"hello\\n\"\n",
      "  file << \"world\"\n",
      "}"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 23,
       "text": [
        "#<File:0x007fc47b50eff0>"
       ]
      }
     ],
     "prompt_number": 23
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "File.open(\"testfile\",\"w\") do |file|\n",
      "  file << \"hello\\n\"\n",
      "  file << \"world\"\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 24,
       "text": [
        "#<File:0x007fc47b4fcff8>"
       ]
      }
     ],
     "prompt_number": 24
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "names = ['Bozhidar', 'Steve', 'Sarah']\n",
      "names.each { |name| puts name.upcase }"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "BOZHIDAR\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "STEVE\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "SARAH\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 25,
       "text": [
        "[\"Bozhidar\", \"Steve\", \"Sarah\"]"
       ]
      }
     ],
     "prompt_number": 25
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "names.select { |name| name.start_with?('S') }.map { |name| name.upcase }"
     ],
     "language": "ruby",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 26,
       "text": [
        "[\"STEVE\", \"SARAH\"]"
       ]
      }
     ],
     "prompt_number": 26
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "ruby",
     "metadata": {},
     "outputs": [],
     "prompt_number": 27
    }
   ],
   "metadata": {}
  }
 ]
}