Add swap to Data.Tuple

[r6]

I think swap is a widely accepted name for the function. There is only the question of strictness. I suggest swap for the lazy version and swap' for the strict version

swap ~(a,b) = (b,a)

swap' (a,b) = (b,a)

[YitzGale]

I would usually spell this

swap = uncurry $ flip (,)

That supports your choice of the lazy version as unprimed.

[MartijnVanSteenbergen]

Whichever version is chosen, I think it should be reexported as part of the Prelude, too.

[YitzGale]

I wrote:

That supports your choice of the lazy version as unprimed.

I now retract that comment, based on discussion in the thread on haskell-cafe:

 http://www.haskell.org/pipermail/haskell-cafe/2009-June/062772.html

I now support the addition of only the strict version:

swap (a, b) = (b, a)

[simonmar]

Replying to YitzGale:

I would usually spell this {{{ swap = uncurry $ flip (,) }}} That supports your choice of the lazy version as unprimed.

I had tongue firmly in cheek when I suggested using this definition on haskell-cafe a while ago. I am not sure whether to be horrified or amused that some people would actually prefer to write it that way!

[MartijnVanSteenbergen]

Maybe a bit of both? :-)

[YitzGale]

I wrote:

swap = uncurry $ flip (,)

simonmar wrote:

I had tongue firmly in cheek when I suggested using this definition on haskell-cafe a while ago. I am not sure whether to be horrified or amused that some people would actually prefer to write it that way!

He he, I didn't even remember that, perhaps I didn't see it.

Anyway, I never meant to suggest that it should actually be written that way in the libraries. Just that the laziness of the natural points-free version is evidence in support of laziness. And I have retracted even that claim.

[igloo]

Looks like an abandoned proposal

[simonmar]

Done:

Tue May  4 10:53:39 BST 2010  Simon Marlow <marlowsd@gmail.com>
  * Add swap (#3298)