From: Robert Klemme <bob.news@...>
Date: 2006-03-25T19:08:53+09:00
Subject: Re: require a certain version of the ruby interpreter

Ross Bamford wrote:
> On Sat, 2006-03-25 at 11:06 +0900, dblack@wobblini.net wrote:
>> Hi --
>>
>> On Sat, 25 Mar 2006, Robert Klemme wrote:
>>
>>> Shea Martin wrote:
>>>> This works nicely, but I am sure something like this is already built in, 
>>>> but I can't seem to find it.
>>>>
>>>> def require_version( p_ver_str )
>>>>   l_have = VERSION.split('.')
>>>>   l_need = p_ver_str.split('.')
>>>>   l_need.each_index do |i|
>>>>     if l_have[i].to_i < l_need[i].to_i
>>>>       raise ScriptError, "Required Ruby #{p_ver_str}, found Ruby 
>>>> #{VERSION}"
>>>>     end
>>>>   end
>>>> end
>>> Hmmm, lettsee whether we can compress that a bit. How about:
>>>
>>> def ensure_version(ver)
>>>  raise "Requiring at least #{ver}" unless
>>>    RUBY_VERSION.scan(/d+/).map! {|x|x.to_i} >=
>>>       ver.scan(/d+/).map! {|x|x.to_i}
>>> end
>>>
>>> Not really a one liner...
>> (What, no inject? :-)  I don't think Array has >= though.

Actually, a version with #inject occurred to me after I sent the other 
one out when I thought about reducing redundancy in the code above - 
you're also right about Array (strange though as it does implement <=>):

def ev(ver)
   raise "Requiring at least #{ver}" unless
     [RUBY_VERSION,ver].map! {|v| v.scan(/\d+/).map! {|x|x.to_i}}.
       inject {|v1,v2| (v1<=>v2)>=0}
end

> :) Even I couldn't find an excuse for inject on this one. The best I
> could do was:
> 
> def ensure_version(v)
>   raise "need #{v}" if VERSION.split('.').zip(v.split('.')).any? {|a,b| a < b}
> end

Nice, too!  I like the approach with any?.

> (given that we don't need to worry about two-digit versions of course).

You could still to the .to_i when comparing.

Kind regards

	robert