Generating negative random numbers

ruby-talk
1

I know how to generate positive random numbers, but is it possible to generate a random number in a range such [-9..+9] ?
tfyh

joss

2

Rand(18)-9

Gerald Ebberink
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···

-----Original Message-----
From: Josselin [mailto:josselin@wanadoo.fr]
Sent: dinsdag 30 januari 2007 8:10
To: ruby-talk ML
Subject: generating negative random numbers

I know how to generate positive random numbers, but is it possible to
generate a random number in a range such [-9..+9] ?
tfyh

joss

3

irb(main):001:0> def rrand(x)
irb(main):002:1> rand(2*x) - x
irb(main):003:1> end
=> nil
irb(main):004:0> rrand 9
=> -7
irb(main):005:0> rrand 9
=> -8
irb(main):006:0> rrand 9
=> 5
irb(main):007:0> rrand 9
=> -8

···

On Jan 29, 2007, at 11:10 PM, Josselin wrote:

I know how to generate positive random numbers, but is it possible to generate a random number in a range such [-9..+9] ?

4

rand(19) - 9

Farrel

···

On 30/01/07, Josselin <josselin@wanadoo.fr> wrote:

I know how to generate positive random numbers, but is it possible to
generate a random number in a range such [-9..+9] ?
tfyh

joss

5

class Range
  def rand
    Kernel::rand(last - first + 1) + first
  end
end

(-9..9).rand

martin

···

On 1/30/07, Josselin <josselin@wanadoo.fr> wrote:

I know how to generate positive random numbers, but is it possible to
generate a random number in a range such [-9..+9] ?
tfyh

6

thanks to all of u, got it, but why there is no 'standard' function in the lib ...

···

On 2007-01-30 08:05:18 +0100, Josselin <josselin@wanadoo.fr> said:

I know how to generate positive random numbers, but is it possible to generate a random number in a range such [-9..+9] ?
tfyh

joss

7

thanks ... I'd never think about it !

···

On 2007-01-30 08:14:39 +0100, "Gerald Ebberink" <g.h.p.ebberink@nclr.nl> said:

Rand(18)-9

Gerald Ebberink
Laser Technician

NCLR B.V.
PO box 2662
Enschede 7500CR
The Netherlands
  Work: 31 53 4891110
Direct: 31 53 4893961
Fax: 31 53 4891102
Email: g.h.p.ebberink@nclr.nl

http://www.linkedin.com/in/geraldebberink

    Want a signature like this?

-----Original Message-----
From: Josselin [mailto:josselin@wanadoo.fr]
Sent: dinsdag 30 januari 2007 8:10
To: ruby-talk ML
Subject: generating negative random numbers

I know how to generate positive random numbers, but is it possible to
generate a random number in a range such [-9..+9] ?
tfyh

joss

8

(-9...10).rand won't give the expected answer. I think the below should fix the problem when the last entry in the range is excluded:

class Range
  def rand
    return first if exclude_end? && last == first
    Kernel::rand(last - first + (exclude_end? ? 0 : 1)) + first
  end
end

···

On Jan 30, 2007, at 08:52 , Martin DeMello wrote:

On 1/30/07, Josselin <josselin@wanadoo.fr> wrote:

I know how to generate positive random numbers, but is it possible to
generate a random number in a range such [-9..+9] ?
tfyh

class Range
def rand
   Kernel::rand(last - first + 1) + first
end
end

(-9..9).rand