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19
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1 day2.rb(main):001:0> #! /usr/bin/env ruby
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2 day2.rb(main):002:0*
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3 day2.rb(main):003:0* ## File handling with a block
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4 day2.rb(main):004:0* name = 'day2.txt'
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5 => "day2.txt"
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6 day2.rb(main):005:0>
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7 day2.rb(main):006:0* def print_file(name)
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8 day2.rb(main):007:1> File.open(name, 'r') do |file|
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9 day2.rb(main):008:2* puts name
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10 day2.rb(main):009:2> while line = file.gets
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11 day2.rb(main):010:3> puts " #{line}"
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12 day2.rb(main):011:3> end
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13 day2.rb(main):012:2> end
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14 day2.rb(main):013:1> end
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15 => :print_file
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16 day2.rb(main):014:0>
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17 day2.rb(main):015:0* File.open(name, 'w') do |file|
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18 day2.rb(main):016:1* file.puts "File contents go here"
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19 day2.rb(main):017:1> end
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20 => nil
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21 day2.rb(main):018:0> print_file(name)
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22 day2.txt
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23 File contents go here
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24 => nil
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25 day2.rb(main):019:0> File.open(name, 'r+') do |file|
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26 day2.rb(main):020:1* # If we don't seek then we override
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27 day2.rb(main):021:1* file.seek(0, IO::SEEK_END)
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28 day2.rb(main):022:1> file.puts 'Extra content here'
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29 day2.rb(main):023:1> end
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30 => nil
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31 day2.rb(main):024:0> print_file(name)
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32 day2.txt
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33 File contents go here
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34 Extra content here
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35 => nil
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36 day2.rb(main):025:0> File.delete(name)
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37 => 1
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38 day2.rb(main):026:0>
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39 day2.rb(main):027:0* puts "File still exists!" if File.exists?(name)
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40 => nil
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41 day2.rb(main):028:0>
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42 day2.rb(main):029:0* # Old-skool Java style without passing a code block
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43 day2.rb(main):030:0* my_file = File.open(name, 'w')
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44 => #<File:day2.txt>
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45 day2.rb(main):031:0> my_file.puts 'Non-block file content'
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46 => nil
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47 day2.rb(main):032:0> my_file.close() #Note: Close the file manually!
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48 => nil
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49 day2.rb(main):033:0> print_file(name)
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50 day2.txt
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51 Non-block file content
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52 => nil
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53 day2.rb(main):034:0> File.delete(name)
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54 => 1
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55 day2.rb(main):035:0>
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56 day2.rb(main):036:0* ## Converting a hash into an array
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57 day2.rb(main):037:0* my_hash = { 'a' => 'one', 'b' => 'two', 'c' => 'three' }
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58 => {"a"=>"one", "b"=>"two", "c"=>"three"}
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59 day2.rb(main):038:0> puts my_hash.inspect
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60 {"a"=>"one", "b"=>"two", "c"=>"three"}
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61 => nil
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62 day2.rb(main):039:0> # "{}.methods" includes "to_a" method - appears to convert to an array.
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63 day2.rb(main):040:0* puts my_hash.to_a.inspect
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64 [["a", "one"], ["b", "two"], ["c", "three"]]
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65 => nil
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66 day2.rb(main):041:0> # However, it includes keys *and* values (as nested arrays, according to http://apidock.com/ruby/Hash/to_a).
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67 day2.rb(main):042:0* # There's also ":keys" and ":values"
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68 day2.rb(main):043:0* puts my_hash.keys.inspect
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69 ["a", "b", "c"]
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70 => nil
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71 day2.rb(main):044:0> puts my_hash.values.inspect
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72 ["one", "two", "three"]
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73 => nil
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74 day2.rb(main):045:0> # Alternatively, :collect runs over all key-value pairs as an array, so we can do:
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75 day2.rb(main):046:0* puts my_hash.collect { |val| val[1] }.inspect
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76 ["one", "two", "three"]
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77 => nil
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78 day2.rb(main):047:0>
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79 day2.rb(main):048:0* ## Converting an array to a hash
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80 day2.rb(main):049:0* # Arrays have a :to_h method, but that assumes nested arrays of key-value pairs,
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81 day2.rb(main):050:0* # e.g. [[key1, value1], [key2, value2]]
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82 day2.rb(main):051:0* # Looping to create a nested array structure then :to_h would work:
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83 day2.rb(main):052:0* my_array = ['one', 'two', 'three']
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84 => ["one", "two", "three"]
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85 day2.rb(main):053:0> temp = []
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86 => []
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87 day2.rb(main):054:0> # This would be neater with :map or :collect but then we don't get the index.
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88 day2.rb(main):055:0* # The only sensible option is an :each_with_index, but that negates the need
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89 day2.rb(main):056:0* # for :to_h.
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90 day2.rb(main):057:0* my_hash = {}
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91 => {}
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92 day2.rb(main):058:0> my_array.each_with_index do |val, idx|
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93 day2.rb(main):059:1* my_hash[idx] = val
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94 day2.rb(main):060:1> end
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95 => ["one", "two", "three"]
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96 day2.rb(main):061:0> puts my_hash.inspect
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97 {0=>"one", 1=>"two", 2=>"three"}
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98 => nil
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99 day2.rb(main):062:0>
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