From: Raphael Clancy <raphael.clancy@...>
Date: 2009-02-15T00:19:40+09:00
Subject: Re: uniuq no

7stud -- wrote:
> Vetrivel Vetrivel wrote:
>> I want to create new unique id in ruby.I have used the following
>> coding.But I don''t know whether it works perfectly or not.
>> 
>>  t = Time.new
>>  p "%10.5f" % t.to_f
>> 
>> does it give unique value always.
> 
> This might be better:
> 
> d = Time.new
> t = d.to_f
> puts t
> 
> r = rand
> puts r
> 
> p_id = $$
> puts p_id
> 
> new_id = t + 10000000 * r + 10000000 * p_id
> p new_id

Be a little careful with this, floats are not very precise, (see: 
http://www.ruby-forum.com/topic/178503 ) and this could lead to some 
duplication.

irb(main):001:0> a = (10.12 * 100).to_i
=> 1011
irb(main):002:0> b = (10.11 * 100).to_i
=> 1011
irb(main):003:0> a == b
=> true

While this really shouldn't be a problem with this scheme, big decimal 
might be safer...

(see: 
http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html 
)
-- 
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