Re: Proposal: Add an analogue of $! to deepseq

The ticket for this is http://hackage.haskell.org/trac/ghc/ticket/5323 On 15 July 2011 08:49, Ivan Lazar Miljenovic wrote:

It's been two weeks since I raised this, and as such discussion time is over.  For the complete discussion, please see http://www.haskell.org/pipermail/libraries/2011-July/016540.html

In total, there were five respondees.

On 1 July 2011 17:55, Ivan Lazar Miljenovic wrote:

...

I propose we add a operator - tentatively labelled $!! (and which Hayoo reports isn't currently exported by a Hackage package) - as a deepseq analogue $! to the deepseq library:

($!!) :: (NFData a) => (a -> b) ->a -> b f $!! x = x `deepseq` f x

infixr 0 $!!

All respondees agreed with this proposal; as such it passes.

...

As a sub-proposal, I also propose that we add a "force" function (the name of which also seems to be unused) to make it easier to test forcing of values:

force :: (NFData a) => a -> a force x = x `deepseq` x

* Two people agreed with this proposal.

* Two people indicated that it may produce confusing results (one of which at least can be seen as a vote against this proposal),

* The fifth respondee didn't mention it.

As such, including myself in the tally, I would consider that this proposal passes, but that we should add sufficient documentation to cover Malcolm's and Sebastian's concerns (specifically that using force inside a left-fold would actually be more analogous to foldl than foldl', and that a reminder should be made that this will evaluate the value to NF rather than HNF, which is indeed the point).

I will now go and create a ticket on the GHC Trac.

@Simon: as the maintainer of deepseq, would you prefer I create a patch with these changes, or will you do so yourself?

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com