From: dblack@...
Date: 2006-03-25T20:59:58+09:00
Subject: Re: require a certain version of the ruby interpreter

Hi --

On Sat, 25 Mar 2006, Robert Klemme wrote:

> 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 <=>):

Indeed.  I don't know why Array doesn't mix in Comparable.

> 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.

Here's yet another variation on the theme.  (I thought I'd posted this
in my previous post but I didn't.)

require 'scanf'
def ensure_version(need)
   need.scanf("%d.%d.%d").
        zip(RUBY_VERSION.scanf("%d.%d.%d")).any? do |a,b|
     a > b
   end and raise "Requires at least #{need}"
end

I know that two digit numbers aren't on the horizon but it still feels
weird to me to do an alphabetical comparison.


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

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