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comparison 1-Ruby/day2-irb.output @ 19:ddcd809319ac

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Add first two Day 2 exercises
author IBBoard <dev@ibboard.co.uk>
date Wed, 04 Jan 2017 21:01:13 +0000
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18:e58952c15e5e 19:ddcd809319ac
1 day2.rb(main):001:0> #! /usr/bin/env ruby
2 day2.rb(main):002:0*
3 day2.rb(main):003:0* ## File handling with a block
4 day2.rb(main):004:0* name = 'day2.txt'
5 => "day2.txt"
6 day2.rb(main):005:0>
7 day2.rb(main):006:0* def print_file(name)
8 day2.rb(main):007:1> File.open(name, 'r') do |file|
9 day2.rb(main):008:2* puts name
10 day2.rb(main):009:2> while line = file.gets
11 day2.rb(main):010:3> puts " #{line}"
12 day2.rb(main):011:3> end
13 day2.rb(main):012:2> end
14 day2.rb(main):013:1> end
15 => :print_file
16 day2.rb(main):014:0>
17 day2.rb(main):015:0* File.open(name, 'w') do |file|
18 day2.rb(main):016:1* file.puts "File contents go here"
19 day2.rb(main):017:1> end
20 => nil
21 day2.rb(main):018:0> print_file(name)
22 day2.txt
23 File contents go here
24 => nil
25 day2.rb(main):019:0> File.open(name, 'r+') do |file|
26 day2.rb(main):020:1* # If we don't seek then we override
27 day2.rb(main):021:1* file.seek(0, IO::SEEK_END)
28 day2.rb(main):022:1> file.puts 'Extra content here'
29 day2.rb(main):023:1> end
30 => nil
31 day2.rb(main):024:0> print_file(name)
32 day2.txt
33 File contents go here
34 Extra content here
35 => nil
36 day2.rb(main):025:0> File.delete(name)
37 => 1
38 day2.rb(main):026:0>
39 day2.rb(main):027:0* puts "File still exists!" if File.exists?(name)
40 => nil
41 day2.rb(main):028:0>
42 day2.rb(main):029:0* # Old-skool Java style without passing a code block
43 day2.rb(main):030:0* my_file = File.open(name, 'w')
44 => #<File:day2.txt>
45 day2.rb(main):031:0> my_file.puts 'Non-block file content'
46 => nil
47 day2.rb(main):032:0> my_file.close() #Note: Close the file manually!
48 => nil
49 day2.rb(main):033:0> print_file(name)
50 day2.txt
51 Non-block file content
52 => nil
53 day2.rb(main):034:0> File.delete(name)
54 => 1
55 day2.rb(main):035:0>
56 day2.rb(main):036:0* ## Converting a hash into an array
57 day2.rb(main):037:0* my_hash = { 'a' => 'one', 'b' => 'two', 'c' => 'three' }
58 => {"a"=>"one", "b"=>"two", "c"=>"three"}
59 day2.rb(main):038:0> puts my_hash.inspect
60 {"a"=>"one", "b"=>"two", "c"=>"three"}
61 => nil
62 day2.rb(main):039:0> # "{}.methods" includes "to_a" method - appears to convert to an array.
63 day2.rb(main):040:0* puts my_hash.to_a.inspect
64 [["a", "one"], ["b", "two"], ["c", "three"]]
65 => nil
66 day2.rb(main):041:0> # However, it includes keys *and* values (as nested arrays, according to http://apidock.com/ruby/Hash/to_a).
67 day2.rb(main):042:0* # There's also ":keys" and ":values"
68 day2.rb(main):043:0* puts my_hash.keys.inspect
69 ["a", "b", "c"]
70 => nil
71 day2.rb(main):044:0> puts my_hash.values.inspect
72 ["one", "two", "three"]
73 => nil
74 day2.rb(main):045:0> # Alternatively, :collect runs over all key-value pairs as an array, so we can do:
75 day2.rb(main):046:0* puts my_hash.collect { |val| val[1] }.inspect
76 ["one", "two", "three"]
77 => nil
78 day2.rb(main):047:0>
79 day2.rb(main):048:0* ## Converting an array to a hash
80 day2.rb(main):049:0* # Arrays have a :to_h method, but that assumes nested arrays of key-value pairs,
81 day2.rb(main):050:0* # e.g. [[key1, value1], [key2, value2]]
82 day2.rb(main):051:0* # Looping to create a nested array structure then :to_h would work:
83 day2.rb(main):052:0* my_array = ['one', 'two', 'three']
84 => ["one", "two", "three"]
85 day2.rb(main):053:0> temp = []
86 => []
87 day2.rb(main):054:0> # This would be neater with :map or :collect but then we don't get the index.
88 day2.rb(main):055:0* # The only sensible option is an :each_with_index, but that negates the need
89 day2.rb(main):056:0* # for :to_h.
90 day2.rb(main):057:0* my_hash = {}
91 => {}
92 day2.rb(main):058:0> my_array.each_with_index do |val, idx|
93 day2.rb(main):059:1* my_hash[idx] = val
94 day2.rb(main):060:1> end
95 => ["one", "two", "three"]
96 day2.rb(main):061:0> puts my_hash.inspect
97 {0=>"one", 1=>"two", 2=>"three"}
98 => nil
99 day2.rb(main):062:0>