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Topic: Random numbers
Replies: 64   Last Post: Dec 24, 2007 1:04 PM

 Messages: [ Previous | Next ]
 Phil Carmody Posts: 2,219 Registered: 12/7/04
Re: Random numbers
Posted: Dec 21, 2007 9:20 AM

quasi <quasi@null.set> writes:
> On 21 Dec 2007 14:53:38 +0200, Phil Carmody
> <thefatphil_demunged@yahoo.co.uk> wrote:
>

> >quasi <quasi@null.set> writes:
> >> On 21 Dec 2007 14:33:08 +0200, Phil Carmody
> >> <thefatphil_demunged@yahoo.co.uk> wrote:
> >>

> >> >John <iamachamp@gmail.com> writes:
> >> >> Given a function that returns a random number between 1-5, write one
> >> >> that returns a random number between 1-7 for the case when it should
> >> >> be integer and for the case it can be real.

> >> >
> >> >int rand1to7i()
> >> >{
> >> > int r1=rand1to5i();
> >> > if(r1==5) { r1+=rand1to5i()/2; }
> >> > return r1;
> >> >}

> >>
> >> Fatally flawed.

> >
> >Wrong. Care to back up your claim? Between you and me, I
> >reckon you've not thought about my response enough.

>
> Yes, do a simulation, and then _you_ think about it.

What do you think the simulation will prove, and why do you
think that's important?

> >> >double rand1to7d()
> >> >{
> >> > return rand1to5d()+(rand1to5d()-1)/2;
> >> >}

> >>
> >> Inefficient -- uses 2 RNG calls, instead of 1.

> >
> >Wrong. If you stretch the numbers out, you'll leave gaps
> >between them, these aren't actual reals, you did realise
> >that, right? You *need* 2 calls to ensure that you leave
> >no gaps.

>
> Forget gaps -- your method is biased!

Phil
--
Dear aunt, let's set so double the killer delete select all.
-- Microsoft voice recognition live demonstration

Date Subject Author
12/21/07 Champ
12/21/07 quasi
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 Marshall
12/21/07 Phil Carmody
12/21/07 quasi
12/21/07 Phil Carmody
12/21/07 Marshall
12/21/07 briggs@encompasserve.org
12/21/07 William Elliot
12/21/07 quasi
12/22/07 William Elliot
12/21/07 Pubkeybreaker
12/21/07 b92057@yahoo.com
12/22/07 quasi
12/21/07 simple.popeye@gmail.com
12/21/07 simple.popeye@gmail.com
12/22/07 quasi
12/22/07 Gib Bogle
12/22/07 quasi
12/21/07 Marshall
12/22/07 simple.popeye@gmail.com
12/22/07 quasi
12/22/07 simple.popeye@gmail.com
12/22/07 quasi
12/22/07 quasi
12/22/07 quasi
12/22/07 simple.popeye@gmail.com
12/22/07 quasi
12/23/07 simple.popeye@gmail.com
12/23/07 simple.popeye@gmail.com
12/23/07 simple.popeye@gmail.com
12/23/07 simple.popeye@gmail.com
12/23/07 simple.popeye@gmail.com
12/22/07 simple.popeye@gmail.com
12/22/07 Herman Rubin
12/22/07 b92057@yahoo.com
12/22/07 quasi
12/23/07 b92057@yahoo.com
12/23/07 quasi
12/23/07 b92057@yahoo.com
12/24/07 quasi
12/24/07 quasi