From: Robert Klemme <shortcutter@...>
Date: 2011-09-20T22:18:55+09:00
Subject: Re: How to generate rand (random number) between two numbers?

On Tue, Sep 20, 2011 at 2:19 PM, Rob Biedenharn
<Rob@agileconsultingllc.com> wrote:
>
> On Sep 19, 2011, at 1:03 PM, Chuck Remes wrote:
>
>>
>> On Sep 19, 2011, at 11:52 AM, Асет Асет wrote:
>>
>>> Hi,
>>>
>>> How to generate rand (random number) between two numbers?
>>> I mean not between 0 and some number. It should be between some number
>>> (not 0) and some number.
>>
>> Try this:
>>
>> irb(main):001:0> def random_number(from, to)
>> irb(main):002:1> from + rand((to - from).abs)
>> irb(main):003:1> end
>> => #<Rubinius::CompiledMethod random_number file=(irb)>
>> irb(main):004:0> random_number(6, 9)
>> => 6
>> irb(main):005:0> random_number(6, 9)
>> => 7
>> irb(main):006:0> random_number(6, 9)
>> => 6
>> irb(main):007:0> random_number(6, 9)
>> => 6
>>
>>
>> cr
>
> Or if you don't mind opening a core class:
> irb1.9.2> class Range
> irb1.9.2>   def sample
> irb1.9.2>     span = self.end - self.begin
> irb1.9.2>     span += 1 unless self.exclude_end?
> irb1.9.2>     self.begin + rand(span.to_i)
> irb1.9.2>     end
> irb1.9.2>   end
> #1.9.2 => nil
> irb1.9.2> (6..9).sample
> #1.9.2 => 7
> irb1.9.2> (6..9).sample
> #1.9.2 => 8
> irb1.9.2> (6..9).sample
> #1.9.2 => 7
> irb1.9.2> (6..9).sample
> #1.9.2 => 9
> irb1.9.2> (6..9).sample
> #1.9.2 => 8
> irb1.9.2> (6..9).sample
> #1.9.2 => 7
> irb1.9.2> (6..9).sample
> #1.9.2 => 6

I mind, because it's tricky to get right:

irb(main):022:0> (0.0..0.1).sample
=> 0.0
irb(main):023:0> (0.0..0.1).sample
=> 0.0
irb(main):024:0> (0.0..0.1).sample
=> 0.0
irb(main):025:0> (0.0..0.1).sample
=> 0.0
irb(main):026:0> (0.0..0.1).sample
=> 0.0
irb(main):027:0> (0.0..0.1).sample
=> 0.0
irb(main):028:0> (0.0..0.1).sample
=> 0.0
irb(main):029:0> (0.0..0.1).sample
=> 0.0
irb(main):030:0> (0.0..0.1).sample

i.e. you always get 0 and

irb(main):057:0> ("a".."o").sample
NoMethodError: undefined method `-' for "o":String
        from (irb):11:in `sample'
        from (irb):57
        from /opt/bin/irb19:12:in `<main>'

At least the logic in Range#sample should be a bit more involved to
either make it fail for floats or only if floats are used with an
inclusive range (..).

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/