From: Axel Etzold <AEtzold@...>
Date: 2008-07-19T20:18:38+09:00
Subject: Re: Finding the date of an event based on related events.


-------- Original-Nachricht --------
> Datum: Sat, 19 Jul 2008 01:20:12 +0900
> Von: Kaldrenon <kaldrenon@gmail.com>
> An: ruby-talk@ruby-lang.org
> Betreff: Finding the date of an event based on related events.

> Hi all,
> 
> I'm doing some planning to write a simple utility program for
> maintaining my schedule. The basic scenario is that, in my job, I have
> a series of multi-stage procedures to perform, and for each instance
> of the procedure, the stages need to happen a fixed number of business
> days apart (i.e, if step one happens on Monday, step two is Friday,
> but if step one is Tuesday, step two will be the following Monday). As
> one of the first steps of the program, I'm going to write a script to
> quickly spit out the calendar dates of all steps given the date of the
> first and the relative date (in business days) of all the others.
> 
> My question is, can you help me drum up a 'smart' way to take weekends
> and holidays into account? I know that with Ruby's Date class you can
> use the - (minus) operator to subtract x days from the date of an
> existing event. which is how I can find the exact date once I've
> determined the number of total days it will be before it has been x
> business days.
> 
> But the "human" solution to the problem isn't very efficient -
> iterating over the days with a counter, checking Date.wday, ignoring
> days that return 0 and 6, and spitting back the date at which the
> counter reaches x. I'd like to find a more elegant and computationally
> efficient solution.
> 
> If you've worked out this problem before, or a better solution seems
> readily available to you, I'd love input. If my explanation was
> unclear, I'll gladly clarify anything.
> 
> -Andrew Fallows

Dear Andrew,

reading previous responses to your post,  I'd like to mention that you can get a list of public holidays from the Wikipedia

http://en.wikipedia.org/wiki/List_of_holidays_by_country,

for many countries, the movable holidays are mostly Easter and Pentecost,
there is a listing of the Easter dates here (and Pentecost is, I believe, just 7 weeks later):

http://www.assa.org.au/edm.html#List20

and, secondly, that for the main task you have -- scheduling --- you could use a "Constraint Programming" framework,
such as this:

http://gecoder.rubyforge.org/

where you input all the conditions you have and get back a solution...

Best regards,

Axel 

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