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Ruby array with strange values

Why the code below sets my @groups array to:

@groups=[[[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]]]

@ groups.inspect shows the weird things above: why? the puts statement in the code below shows the expected 0..35 . @groups triggered using nil for all elements when this code is run.

 class Os_tasks def set_n_tasks(n) @n_tasks=n end def set_n_events(n) @n_events=n end def create_group_sizes @ n_groups=@n _tasks / @n_events even=@n _groups*@n_events n_expanded_groups=@n _tasks-even @group_sizes = [] added_groups=n_expanded_groups ( 0..@n _groups-1).each do x=0 if added_groups > 0 x=1 added_groups=added_groups-1 end x=x+@n _events @group_sizes << x end end def create_groups @groups=Array.new(@n_events) e_groups=Array.new(@n_groups) ( 0..@n _events-1).each do |i| ( 0..@n _groups-1).each do |j| e_groups[j]=Array.new(@group_sizes[j]) end @groups[i]=e_groups end end def init_groups x=0 @groups.each_index do |i| @groups[i].each_index do |j| @groups[i][j].each_index do |k| @groups[i][j][k]=x puts "i:" + i.to_s + ", j:" + j.to_s + ", k:" + k.to_s + ", x:" + x.to_s + " @groups[" + i.to_s + "][" + j.to_s + "][" + k.to_s + "]: " + @groups[i][j][k].to_s x = x + 1 end end end end end gtask = Os_tasks.new puts "Number of task groups: " gtask.set_n_tasks(gets.chomp.to_i) puts "Number of events: " gtask.set_n_events(gets.chomp.to_i) gtask.create_group_sizes gtask.create_groups gtask.init_groups puts gtask.inspect

This baby is launched below: (check at the end)

 Number of tasks: 12 Number of events: 3 i:0, j:0, k:0, x:0 @groups[0][0][0]: 0 i:0, j:0, k:1, x:1 @groups[0][0][1]: 1 i:0, j:0, k:2, x:2 @groups[0][0][2]: 2 i:0, j:1, k:0, x:3 @groups[0][1][0]: 3 i:0, j:1, k:1, x:4 @groups[0][1][1]: 4 i:0, j:1, k:2, x:5 @groups[0][1][2]: 5 i:0, j:2, k:0, x:6 @groups[0][2][0]: 6 i:0, j:2, k:1, x:7 @groups[0][2][1]: 7 i:0, j:2, k:2, x:8 @groups[0][2][2]: 8 i:0, j:3, k:0, x:9 @groups[0][3][0]: 9 i:0, j:3, k:1, x:10 @groups[0][3][1]: 10 i:0, j:3, k:2, x:11 @groups[0][3][2]: 11 i:1, j:0, k:0, x:12 @groups[1][0][0]: 12 i:1, j:0, k:1, x:13 @groups[1][0][1]: 13 i:1, j:0, k:2, x:14 @groups[1][0][2]: 14 i:1, j:1, k:0, x:15 @groups[1][1][0]: 15 i:1, j:1, k:1, x:16 @groups[1][1][1]: 16 i:1, j:1, k:2, x:17 @groups[1][1][2]: 17 i:1, j:2, k:0, x:18 @groups[1][2][0]: 18 i:1, j:2, k:1, x:19 @groups[1][2][1]: 19 i:1, j:2, k:2, x:20 @groups[1][2][2]: 20 i:1, j:3, k:0, x:21 @groups[1][3][0]: 21 i:1, j:3, k:1, x:22 @groups[1][3][1]: 22 i:1, j:3, k:2, x:23 @groups[1][3][2]: 23 i:2, j:0, k:0, x:24 @groups[2][0][0]: 24 i:2, j:0, k:1, x:25 @groups[2][0][1]: 25 i:2, j:0, k:2, x:26 @groups[2][0][2]: 26 i:2, j:1, k:0, x:27 @groups[2][1][0]: 27 i:2, j:1, k:1, x:28 @groups[2][1][1]: 28 i:2, j:1, k:2, x:29 @groups[2][1][2]: 29 i:2, j:2, k:0, x:30 @groups[2][2][0]: 30 i:2, j:2, k:1, x:31 @groups[2][2][1]: 31 i:2, j:2, k:2, x:32 @groups[2][2][2]: 32 i:2, j:3, k:0, x:33 @groups[2][3][0]: 33 i:2, j:3, k:1, x:34 @groups[2][3][1]: 34 i:2, j:3, k:2, x:35 @groups[2][3][2]: 35 #<Os_tasks:0x28b1428 @n_tasks=12, @n_events=3, @n_groups=4, @group_sizes=[3, 3, 3, 3], @groups=[[[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]]]>
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1 answer

The problem is here:

 def create_groups @groups=Array.new(@n_events) e_groups=Array.new(@n_groups) ( 0..@n _events-1).each do |i| ( 0..@n _groups-1).each do |j| e_groups[j]=Array.new(@group_sizes[j]) end @groups[i]=e_groups end end

In this method, you have an e_groups variable length storage array, and each ( 0..@n _events-1).each do |i| you reinitialize its array elements with nil , and then assign a reference to the same array instance before groups[i] . This is equal to @groups = [e_groups, e_groups, e_groups] .

And then in your init_groups method init_groups you reassign the values ​​of the same array 3 times:

 # i = 0 [[[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]], [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]], [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]]] # i = 1 [[[12, 13, 14], [15, 16, 17], [18, 19, 20], [21, 22, 23]], [[12, 13, 14], [15, 16, 17], [18, 19, 20], [21, 22, 23]], [[12, 13, 14], [15, 16, 17], [18, 19, 20], [21, 22, 23]]] # i = 2 [[[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]], [[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]]]

Decision:

 def create_groups @groups=Array.new(@n_events) ( 0..@n _events-1).each do |i| e_groups=Array.new(@n_groups) # re-initialize e_groups ( 0..@n _groups-1).each do |j| e_groups[j]=Array.new(@group_sizes[j]) end @groups[i]=e_groups end end
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Source: https://habr.com/ru/post/1395589/

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