Re: Unpack primitive types by default in data

On 28/02/2012 15:56, Johan Tibell wrote:

On Tue, Feb 28, 2012 at 1:11 AM, Simon Marlow wrote:

...

I think there are some in GHC - I've been surprised occasionally when adding an UNPACK makes things worse.

I just realized that there is a failure mode I didn't quite consider: having a mix of strict and non-strict primitive fields. While this can happen on purpose, I think it happens more often due to non-strict being the default. Having a field with such a mix might lead to more re-boxing.

(I think you meant "record", not "field" in the last sentence, right?) It's not obvious to me why having a mixture of strict and nonstrict (maybe you meant UNPACKed and not UNPACKed?) fields would make things worse. Could you give a concrete example? Cheers, Simon