From: Robert Klemme <shortcutter@...>
Date: 2009-12-11T02:08:22+09:00
Subject: Re: Fill gaps in Array of Hashes

2009/12/10 Aldric Giacomoni <aldric@trevoke.net>:
> Joao Silva wrote:
>> I have the following object as a result from MySQL:
>>
>> [{:positive=>"0", :neutral=>"2", :total=>"5", :date=>"2009-12-01",
>> :negative=>"3"}, {:positive=>"3", :neutral=>"3", :total=>"7",
>> :date=>"2009-12-08", :negative=>"1"}, {:positive=>"1", :neutral=>"1",
>> :total=>"3", :date=>"2009-12-09", :negative=>"1"}]
>>
>> I want to fill gaps (for example from 2009-11-19 till 2010-10-01) with
>> {:positive=>"0", :neutral=>"0", :total=>"0", :date=>"HEREDATE",
>> :negative=>"1" - how i can do this in ruby? In MySQL it's impossible to
>> do :-(.
>
> Well, the dumb, brute-force way to do it would be something like this, I
> guess:
>
> # Assuming your array is called 'array'
> require 'rubygems'
> require 'activesupport' # What? I'm lazy. to_date is damn handy.
>
> ("2009-11-19".to_date.."2010-10-01".to_date).each do |date|
>  exists = array.find { |x| x[:date] == date.to_s }
>  next if exists # If the date is found in the array, next date please.
>  array << { :positive => "0", :neutral => "0", :total => "0", :date =>
> date,
>             :negative => "1" }
> end

Here's a different approach - not with dates though.

# just an example
def next_val(x)
  x + 2
end

with_gaps = Array.new(10) { rand(40) * 2 }

puts "before"
p with_gaps

with_gaps.sort.each_cons 2 do |a,b|
  next if a == b
  x = a

  while (x = next_val(x)) != b
    with_gaps << x
  end
end

puts "after"
p with_gaps.sort

# automated check
with_gaps.sort.each_cons 2 do |a,b|
  raise("Wrong distance %s" % [a,b].inspect) unless a == b || next_val(a) == b
end

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
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