From: Mark Hubbart <discord@...>
Date: 2004-04-24T02:37:57+09:00
Subject: Re: find a best version (of a package)


On Apr 23, 2004, at 5:17 AM, saiph wrote:

>
> hi list,
>
>
> i'm following the "learning ruby" path, i've found this list very 
> usefull the
> last time (tnx), so i thought to send this simple example to better
> understand what'd to be a good programming style.
>
>
>
> alea> expand -t 2 best_vv
> -----------------------------------------------
> class String
> def newer?(s)
>   b = self.dup
>
>   b.sub!(/(\w+-)/, '')
>   t = $+
>   s.sub!(/(\w+-)/, '')
>
>   return -1 if t != $+  # not the same package
>
>   while (b.sub!(/(\d+\.|\d+)/, '')) do
>     t = $+.chomp('.')
>     s.sub!(/(\d+\.|\d+)/, '')
>
>     return 1 if $+ == nil
>     return 1 if t.to_i > $+.chomp('.').to_i
>   end
>
>   return 0
> end
> end
>
> class Array
> def best_version?
>   s = 0
>
>   for i in 1..self.length() - 1 do
>     t = self[i].newer? self[s]
>     if t == 1
>       s = i
>     elsif t == -1
>       return nil
>     end
>   end
>
>   return s
> end
> end
>
> vv = ['ruby-2.2.5', 'ruby-3.2.6', 'ruby-5']
> i = vv.best_version?
> puts vv[i]
> -----------------------------------------------
>
> how would you write or change this?

first, I would suggest more comments in the code :) at least something 
above the method telling what it does. That makes it so others can see 
at a glance what it is for, and rdoc can document it properly.

query methods (foo?()) generally return true/false. Also, I suspect 
that comparing different packages should raise an error, not return -1.

Otherwise, I think maybe it could be condensed down a bit...

   class String
     # compares package version strings
     def newer?(other)
       this, that = split(/-/), other.split(/-/)

       # check that package names match
       if this[0] != that[0]
       	raise ArgumentError, "package names do not match"
       end

       # compare each section
       this[1].split(".").zip( that[1].split(".") ) do |a,b|
         a, b = a.to_i, b.to_i
         return a > b if a != b
       end

       # neither one was larger:
       return false
     end
   end

   class Array
     # returns the highest version string in an array
     def best_version
       inject{|a,b| a.newer?(b) ? b : a }
     end
   end

cheers,
--Mark