From: Laurent Colloud <fifoooo@...>
Date: 2006-08-15T06:04:46+09:00
Subject: Consecutive sort on Array of Hashes

Hi,

Here my - strange - problem.

To explain it, let's take the example of football. I construct an array 
of hashes of the results with team_id, total of pts, number of wins, 
number of draws and number of defeats such as:

myArray = Array.new
myArray << {:team_id=>1, :pts=>5, :w=>0,  :d=>5, :l=>5}
myArray << {:team_id=>2, :pts=>7, :w=>1,  :d=>4, :l=>5}
myArray << {:team_id=>3, :pts=>4, :w=>0,  :d=>4, :l=>6}
myArray << {:team_id=>4, :pts=>6, :w=>1,  :d=>3, :l=>6}
myArray << {:team_id=>5, :pts=>5, :w=>0,  :d=>5, :l=>5}
myArray << {:team_id=>6, :pts=>5, :w=>0,  :d=>5, :l=>5}
myArray << {:team_id=>8, :pts=>10, :w=>2,  :d=>4, :l=>4}
myArray << {:team_id=>9, :pts=>5, :w=>1,  :d=>2, :l=>7}
myArray << {:team_id=>10, :pts=>8, :w=>1,  :d=>5, :l=>4}
myArray << {:team_id=>11, :pts=>9, :w=>2,  :d=>3, :l=>5}
myArray << {:team_id=>12, :pts=>6, :w=>1,  :d=>3, :l=>6}
myArray << {:team_id=>13, :pts=>5, :w=>0,  :d=>5, :l=>5}

Now, from this array, I want to get the table.
So what I want to do is to sort the array,  first by total of pts, then 
by number of wins (if 2 teams have the same total of points I put first 
the team with more wins) and then by number of draws.

That's how - logically - I would do it anyway. But that does not seem to 
be the Ruby way. Doing it that way gives me a complete mess.

No worries, doing it the other way round works (first sort by draw, then 
wins, then pts)! Here is what I run:

puts "Team, Pts, W, D, L"
myArray = myArray.sort { |a,b| b[:d] <=> a[:d]
		}.sort { |a,b| b[:w] <=> a[:w]
		}.sort { |a,b| b[:pts] <=> a[:pts]
		}.each do |row|
puts "#{row[:team_id]}, #{row[:pts]}, #{row[:w]}, #{row[:d]}, 
#{row[:l]}"
end

Did I say it works? Well almost! Here is my output:

Team, Pts, W, D, L
8, 10, 2, 4, 4
11, 9, 2, 3, 5
10, 8, 1, 5, 4
2, 7, 1, 4, 5
4, 6, 1, 3, 6
12, 6, 1, 3, 6
16, 5, 0, 5, 5
1, 5, 0, 5, 5
9, 5, 1, 2, 7
5, 5, 0, 5, 5
6, 5, 0, 5, 5
3, 4, 0, 4, 6

Good news, we kept the correct team_is with the correct result.
But can anyone explain me what on earth is the line 9, 5, 1, 2, 7 doing 
there in the middle?

Thanks for your help!

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