Thanks, all.

It seemed like something like this should exist in a prob/stat package, and if so, didn't want to reinvent the wheel.

Shuffle [1..20], then take 5?

Yes, so simple, I'm embarrassed I didn't think of it.

Michael

--- On Mon, 6/13/11, Felipe Almeida Lessa <felipe.lessa@gmail.com> wrote:

From: Felipe Almeida Lessa <felipe.lessa@gmail.com>
Subject: Re: [Haskell-cafe] Acquiring a random set of a specific size (w/o dups) from a range of Ints
To: "michael rice" <nowgate@yahoo.com>
Cc: haskell-cafe@haskell.org
Date: Monday, June 13, 2011, 9:38 PM

On Mon, Jun 13, 2011 at 8:56 PM, michael rice <nowgate@yahoo.com> wrote:
> Is there an (existing) way to select 5 Ints randomly (no duplicates) from a population, say 1-20 (inclusive)?

Yes, already implemented in the monte-carlo package as sampleSubset [1],

sampleSubset :: MonadMC m => [a] -> Int -> m [a]

Complete example code for your example:

evalMC (sampleSubset [1..20] 5) (mt19937 0)

Cheers!

[1] http://hackage.haskell.org/packages/archive/monte-carlo/0.4.1/doc/html/Control-Monad-MC-Class.html#v:sampleSubset

--
Felipe.