From: Siep Korteling <s.korteling@...>
Date: 2009-07-11T08:20:58+09:00
Subject: Re: calculating an array of dates

Eric Peterson wrote:
> 
> I have the following test script.  My objective is to have an array of
> dates between this week's Thursday and some date in the past that I get
> out of a call to a database.  You can see the output below which is not
> what I wanted.  I am thinking it is in the way I return data and call my
> recursive routine.  What am I missing?
> 
> 
> I am hoping for data like, which later I can loop through:
> 
> [ [Thu Jul 09 12:00:00 -0700 2009],
>   [Thu Jul 02 12:00:00 -0700 2009],
>   [Thu Jun 25 12:00:00 -0700 2009],
>   [Thu Jun 18 12:00:00 -0700 2009],
>   [Thu Jun 11 13:14:44 -0700 2009] ]
> 
> 
> Thanks for any help ya'll can provide.
> Eric
> 
> 
> 
>>>>>>>>start<<<<<<<<<<<
> require 'rubygems'
> require 'Chronic'
> require 'Time'
> 
> 
> # ---------- ---------- ---------- ---------- ---------- ----------
> def get_weeks( this_dt, max_dt )
> # ---------- ---------- ---------- ---------- ---------- ----------
> # recursively calculate thursdays
> # ---------- ---------- ---------- ---------- ---------- ----------
> 
>   return this_dt.to_a if ( this_dt.strftime( "%Y%m%b" ) ==
> max_dt.strftime( "%Y%m%b" ) )
> puts "get_week_list(): 4. this_dt: #{this_dt.inspect}"
> puts "get_week_list(): 5. max_dt: #{max_dt.inspect}"
> 
>   next_dt = Chronic.parse( 'Last Thursday at noon', :now => this_dt )
> puts "get_week_list(): 6. next_dt: #{next_dt.inspect}\n\n"
>   return get_weeks( next_dt, max_dt ).to_a
> 
> end # get_weeks
> 
> 
> 
> # ---------- ---------- ---------- ---------- ---------- ----------
> def get_week_list( u_id )
> # ---------- ---------- ---------- ---------- ---------- ----------
> # return an array of dates between now and when this user was created
> # ---------- ---------- ---------- ---------- ---------- ----------
> 
>   # ---------- ---------- ----------
>   # what is this week's "end point".
>   # Either today or calculated
>   # ---------- ---------- ----------
>   this_week_end = Time.now
> puts "get_week_list(): Today's day: #{this_week_end.wday.to_s}"
>   if Time.now.wday != 4 # not thursday
> 
>     this_week_end = Chronic.parse( 'Last Thursday at noon', :now =>
> Time.now )
> 
>   end
> puts "get_week_list(): 1. this_week_end: #{this_week_end.inspect}"
> 
>   # ---------- ---------- ----------
>   # How far back should we get a list?
>   # How about to when this user was created?
>   # ---------- ---------- ----------
>   max_date = Time.parse( 'Thu Jun 11 13:14:44 -0700 2009' ) # from a db
> call
> puts "get_week_list(): 2. max_date's day: #{max_date.wday.to_s}"
>   if max_date.wday != 4
> 
>     max_date = Chronic.parse( 'Last Thursday at noon', :now => max_date
> )
> 
>   end
> puts "get_week_list(): 3. max_date: #{max_date.inspect}\n\n"
> 
>   # ---------- ---------- ----------
>   # recursively calc between the two
>   # ---------- ---------- ----------
>   dates = Array.new
>   dates << get_weeks( this_week_end, max_date )
>   return dates
> 
> end # get_week_list
> 
> 
> 
> 
> # --------------------------------------------------------------------
> dts = Array.new
> dts << get_week_list( 2 )
> puts dts.inspect
> puts dts.class
>>>>>>>>end<<<<<<<<<<<
> 
> 
> 
> returns:
> 
> C:\A\ruby>ruby w.rb
> get_week_list(): Today's day: 5
> get_week_list(): 1. this_week_end: Thu Jul 09 12:00:00 -0700 2009
> get_week_list(): 2. max_date's day: 4
> get_week_list(): 3. max_date: Thu Jun 11 13:14:44 -0700 2009
> 
> get_week_list(): 4. this_dt: Thu Jul 09 12:00:00 -0700 2009
> get_week_list(): 5. max_dt: Thu Jun 11 13:14:44 -0700 2009
> get_week_list(): 6. next_dt: Thu Jul 02 12:00:00 -0700 2009
> 
> get_week_list(): 4. this_dt: Thu Jul 02 12:00:00 -0700 2009
> get_week_list(): 5. max_dt: Thu Jun 11 13:14:44 -0700 2009
> get_week_list(): 6. next_dt: Thu Jun 25 12:00:00 -0700 2009
> 
> [[[0, 0, 12, 25, 6, 2009, 4, 176, true, "Pacific Daylight Time"]]]
> Array

I have not looked into the reasons why your code doesn't work, just took 
your post as a coding exercise. My try looks like this:

require 'Date'
class Date
  def thursdays_upto_now
     end_date = Date.today
     res = []
     # get the last thursday:
     end_date -= 1 while (end_date.wday != 4)
     end_date.step(self, -7) do |date|
       res << date
     end
     res
   end
 end

start_date = Date.parse( 'Thu Jun 11 13:14:44 -0700 2009' )
start_date.thursdays_upto_now.each{|thursday| puts thursday.to_s} # or 
whatever

I was happy finding out Date has a step method.

hth, I had some fun,

Siep
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