From: 7stud -- <bbxx789_05ss@...>
Date: 2011-05-01T06:34:59+09:00
Subject: Re: question about working with dates

7stud -- wrote in post #995994:
> eggman2001 wrote in post #995956:
>> I have a list (in database) of weekday non-holiday dates that goes
>> from present back to 1990. From this list, I'd like to pull out dates
>> given different kinds of criteria and add them to an array. Examples
>> of criteria are:
>> - first day of the month for the most recent 5 years. Perhaps obvious,
>> but the first weekday non-holiday of the month isn't necessarily day 1
>> (i.e. 5/1).
>>
>
> All it takes is a little math:
>
>
> require 'date'
>
> #Create array of all weekday dates for last five years
> #(probably faster than pulling them out of a database):
>
> date_arr = []
> previous_years = 5
>

Hmmmm...looks like the following line got deleted somehow:

today = Date.today

>
> 1.upto(previous_years * 365) do |i|
>   new_date = today - i
>
>   next if [6,0].include?(new_date.wday)
>   date_arr << new_date
> end
>

========

>
> You could benchmark whether adding the check below would be faster:
>
>   last_result = results[-1]
>
>   if last_result.is_a?(Date) and last_result.month == month
>      next
>   end

This would be better:

  last_result = results[-1]

  begin
    next if last_result.month == month
  rescue NoMethodError
    #do nothing
  end

That rescue handles the initial case when the results array is empty, 
and results[-1] returns nil.  After the array has one element, then only 
the if check will be executed.

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