Create array from given array - arrays

Question

Is it possible to create an Array from another Array?
Lang: Ruby on Rails
Case
Workers are entitled to fill in their own work hours. Sometimes they forget to do it. This is what I want to tackle. In the end, I want an Array with time codes of periods the worker forgot to register his hours.
timecodes = [201201, 201202, 201203, 201204, 201205, 201206, 201207, 201208, 201209, 201210, 201211, 201212, 201213, 201301, 201302, 201304, 201305, 201306, ...]
Worker works from 201203 to 201209 with us.
timecards = [201203, 201204, 201205, 201207, 201208, 201209]
As you see, he forgot to register 201206.
What I want to do
# Create Array from timecode on start to timecode on end
worked_with_us = [201203, 201204, 201205, 201206, 201207, 201208, 201209]
#=> This is the actual problem, how can I automate this?
forgot_to_register = worked_with_us.?????(timecards)
forgot_to_register = worked_with_us - timecards # Thanks Zwippie
#=> [201206]
Now I know which period the worker forgot to register his hours.
All together
How can I create an Array from another Array, giving a start and end value?

Answer 1

You can just subtract arrays with - (minus):
[1, 2, 3] - [1, 3] = [2]
To build an array with years/months, this can be done with a Range, but this only works if you build an array for each year, something like:
months = (2012..2013).map do |year|
("#{year}01".."#{year}12").to_a.collect(&:to_i)
end.flatten
=> [201201, 201202, 201203, 201204, 201205, 201206, 201207, 201208, 201209, 201210, 201211, 201212, 201301, 201302, 201303, 201304, 201305, 201306, 201307, 201308, 201309, 201310, 201311, 201312]
And for the function to create those ranges dynamically:
def month_array(year_from, year_to, month_from=1, month_to=12)
(year_from..year_to).map do |year|
# Correct from/to months
mf = year_from == year ? month_from : 1
mt = year_to == year ? month_to : 12
(mf..mt).map do |month|
("%d%02d" % [year, month]).to_i
end
end.flatten
end
Update: You wanted other input parameters for this method, but I hope you can work that out yourself. :)