From: Josselin <josselin@...>
Date: 2007-10-31T08:15:09+09:00
Subject: Re: RUBY DRY to replace 6 lines in 1

On 2007-10-30 19:41:09 +0100, MenTaLguY <mental@rydia.net> said:

> On Wed, 31 Oct 2007 01:50:08 +0900, Josselin <josselin@wanadoo.fr> wrote:
>> I have a group of lines  (used in Googlemaps display)  based on 2 arrays :
>> 
>> zl = 9 if farthest_proposition.distance_to(origin) < = 25.0
>> zl = 10 if farthest_proposition.distance_to(origin) <= 15.0
>> zl = 11 if farthest_proposition.distance_to(origin) <= 10.0
>> zl = 12 if farthest_proposition.distance_to(origin) <= 5.0
>> zl = 13 if farthest_proposition.distance_to(origin) < =2.0
>> zl = 14 if farthest_proposition.distance_to(origin) <= 1.0
>> 
>> how could I replace it the dryest way possible ?
>> 
>> zl = [9, 10, 11, 12, 13, 14]
>> distance = [1.0, 2.0, 5.0, 10.0, 15.0, 25.0]
>> farthest_proposition.distance_to(origin) is never > 25 (eliminated
>> before..)
>> farthest_proposition.distance_to(origin)  can be 0.0, never negative
> 
> FWIW, one line isn't necessarily a realistic goal; DRY doesn't always
> mean a large savings in LOC, just maintainability (which an excessively
> "golfed" solution can hurt) and often performance.
> 
> Assuming two arrays given above are called ZL and DISTANCE (they should
> really be constants), one solution is:
> 
>  farthest_distance = farthest_proposition.distance_to(origin)
>  zl = DISTANCE.zip(ZL.reverse).find { |distance, _|
>    farthest_distance <= distance
>  }.first
> 
> Note that eliminating the repeated calls to #distance_to will yield
> a performance increase.  You could also gain additional performance
> by combining ZL and DISTANCE into an associative list:
> 
>  # (distance, z1) sorted by distance
>  ZL_BY_DISTANCE = [
>    [ 1.0,  14 ],
>    [ 2.0,  13 ],
>    [ 5.0,  12 ],
>    [ 10.0, 11 ],
>    [ 15.0, 10 ],
>    [ 25.0, 9  ]
>  ]
> 
> ..at which point you could simply write:
> 
>  farthest_distance = farthest_proposition.distance_to(origin)
>  zl = ZL_BY_DISTANCE.find { |distance, _|
>    farthest_distance <= distance
>  }.first
> 
> (Side note: you might want to consider avoiding lower-case l in
> variable names if you can; it is hard to tell apart from the number 1
> in many fonts.)
> 
> -mental

thanks a  lot... I wrote that in my Ruby Notebook ! I'll keep it in 
mind when coding.. I learned Ruby (because of Rails...)  on my personal 
desk, I need to progress
what are the best books beside the basic ones I have...  to improve 
Ruby coding ?

joss