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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 9:16 AM

quasi <quasi@null.set> writes:
> On Fri, 21 Dec 2007 07:43:48 -0500, quasi <quasi@null.set> wrote:
>

> >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.
> >

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

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

>
> Forget inefficiency -- it's worse than that.
>
> It's biased.

Since when what being unbiased in the requirements?

> >>> 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.

I'm really trying hard, but I just can't see any mention
of the required distribution at all. Can you?

Usenet, I always do.

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