From: Stefano Crocco <stefano.crocco@...>
Date: 2007-09-20T03:24:58+09:00
Subject: Re: special Array method about Unix pathes

Alle mercoled� 19 settembre 2007, Une B�vue ha scritto:
> here is the goal:
>
> i've an Array of Unix pathes :
> forbidden = ["/Volumes/U3 System",
>              "/Volumes/EMTEC KEY/emtec_dl",
>              "/Volumes/EMTEC KEY/emtec_dl/Win98SE new driver.exe",
>              "/Volumes/EMTEC KEY/emtec_dl/v233r001"
>             ]
>
> i want to forbid access to those pathes BUT since, for example,
> "/Volumes/EMTEC KEY/emtec_dl/Win98SE new driver.exe" � belongs �
> to the path (it's below this path) "/Volumes/EMTEC KEY/emtec_dl"
> it is unusefull to have it in the Array.
>
> in the case above i'd like to return :
>
> forbidden = ["/Volumes/U3 System",
>              "/Volumes/EMTEC KEY/emtec_dl"
>             ]
>
> what i've done :
>
>
> class Array
>    def includePath?(path)
>      self.each { | x |
>        return true if path.startsWith?(x)
>      }
>      return false
>    end
>    def getContainers!
>      self.delete_if { | x | ( self - [ x ] ).includePath?( x ) }
>    end
> end
>
> class String
>   def startsWith?(dir)
>     self.index(dir) === 0
>   end
> end
>
> then forbidden.getContainers! gives me the expected result.
>
> what do you think about this solution ?
> could you propose a better one ?
>
> also, because english isn't my mother tongue, are my methods naming
> correct ?

This is my alternative solution:

def select_toplevel_paths arg
  a = arg.dup.sort_by{|i| i.size}                     
  a.inject([]) do |res, i|                            
    res.any?{|j| i.index(j) == 0 } ? res : (res << i) 
  end
end

It doesn't change the contents of the array and it's not a method of class 
Array, because, in my opinion, it's a too specialized method to be put in a 
core class.

Regarding your code, I'd say names are correct, as far as English is 
concerned. I'd like to give you a copule of suggestions:
* use underscores instead of camel-case (include_path? instead of includePath, 
for example), because it's the more common style in the ruby community
* use start_with? instead of starts_with?. In the ruby standard library, there 
are several cases in which both methods exist, with the ones ending in s being 
obsolete (for example, File.exists? and File.exist?) For consistency, I think 
it's better to follow the same convention.

Stefano