On 18 March 2010 04:03, Alexander Solla <ajs@2piix.com> wrote:

On Mar 17, 2010, at 8:33 PM, zaxis wrote:

`allPairs list = [(x,y) | x <- list, y <- list] ` is not what `combination`
does !

let allPairs list = [(x,y) | x <- list, y <- list]
allPairs [1,2,3]

[(1,1),(1,2),(1,3),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3)]

Yeah, I know that. I said so specifically. combination computes the power set of a list. You said your goal was to compute a set of "two groups". You don't need the power set in order to compute a set of pairs. Moreover, computing the power set is a slow operation. Indeed, it is the source of your slowness.

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