From: Josselin <josselin@...>
Date: 2007-08-22T15:54:59+09:00
Subject: Re: splitting Array - DRY

On 2007-08-20 09:56:02 +0200, "Robert Klemme" 
<shortcutter@googlemail.com> said:

> 2007/8/20, Josselin <josselin@wanadoo.fr>:
>> On 2007-08-19 09:58:46 +0200, Stefan Rusterholz <apeiros@gmx.net> said:
>> 
>>> Josselin wrote:
>>>> I am presently splitting an array on 4 successives periods of time , is
>>>> there a DRYest way to do it, or that's the way to go ?  thanks
>>>> 
>>>> @ads_id_w1 = advertisings.map {|ad| ad.id if ((ad.valid_until -
>>>> ad.created_at) / 86400.0 <= 7)}.compact
>>>> 
>>>> @ads_id_w2 = advertisings.map {|ad| ad.id if (((ad.valid_until -
>>>> ad.created_at) / 86400.0 > 7) && ((ad.valid_until - ad.created_at) /
>>>> 86400.0 <= 14)) }.compact
>>>> 
>>>> @ads_id_w3 = advertisings.map {|ad| ad.id if (((ad.valid_until -
>>>> ad.created_at) / 86400.0 > 14) && ((ad.valid_until - ad.created_at) /
>>>> 86400.0 <= 21)) }.compact
>>>> 
>>>> @ads_id_w4 = advertisings.map {|ad| ad.id if (((ad.valid_until -
>>>> ad.created_at) / 86400.0 > 21) && ((ad.valid_until - ad.created_at) /
>>>> 86400.0 <= 31)) }.compact
>>> 
>>> class ClassOfAd
>>> def week # may want to name it differently
>>> return nil unless whateverdate.between?(acceptable_start,
>>> acceptable_end) # your call here
>>> ((ad.valid_until - ad.created_at).div(604800)) % 4
>>> end
>>> @ads_id = Array.new(4) { [] }
>>> advertisings.each {|ad| @ads_id[ad.week] = ad.id if ad.week }
>>> 
>>> Depending on your needs that code can be condensed a bit more.
>>> 
>>> Regards
>>> Stefan
>> 
>> thanks Stefan, I realize that, too frequently, I am programming Ruby as
>> C ..  not using the OO potential
>> what's one of the best book about "Programming Ruby, the way it should
>> be..."  ?
>> I need to practise outside my app dev
>> 
>> note : also found that the  'week' has been already written.. :
>> (ad.valid_until - ad.created_at) >= 2.weeks
> 
> Basically you need a more generalized version of partition. Maybe
> something like this works:
> 
> @ads_id = advertisings.inject(Hash.new {|h,k| h[k]=[]}) do |h,ad|
>   h[(((ad.valid_until - ad.created_at) / 86400 - 1) / 7] << ad.id
>   h
> end
> 
> Note, I'm using interger arithmetic to reduce the number of result values.
> 
> Kind regards
> 
> robert

Thanks Robert... I'll put it in my Personal Ruby Cookbook, that's DRYissimo !