[pypy-dev] More strategies

[Maciej Fijalkowski]

On Thu, Nov 14, 2013 at 11:07 PM, Armin Rigo <arigo at tunes.org> wrote:
> Hi Antonio,
>
> On Thu, Nov 14, 2013 at 2:35 PM, Antonio Cuni <anto.cuni at gmail.com> wrote:
>> W_FloatObjectPresevingTheBits will be created only by operations like
>> struct.unpack, cffi.cast, etc.
>
> That's not enough: if you read one such float into a variable and then
> append that variable into another list, then the other list also needs
> to record the fact that it contains special NaNs.
>
> It seems we could pick the following solution instead: keep
> FloatStrategy, storing a RPython list of floats --- including possibly
> special NaNs; and add FloatIntStrategy, which cannot store special
> NaNs.  We check for the special NaNs when we add into a
> FloatIntStrategy list, and when converting from FloatStrategy to
> FloatIntStrategy.  For the latter case we do indeed need to check all
> items, which sounds a bit pointless, but (1) this is already a good
> progress over the current situation, which is that we need to allocate
> a W_FloatObject per item and a new RPython list to hold them; and (2)
> doing the check over all items upon conversion is actually the same
> total amount of work as it would be if we checked each item as it was
> added to the FloatStrategy list.
>
> (Fwiw, I'm also fond of the idea that it should actually be a
> "FloatIntNoneStrategy"; it would improve the situation even for lists
> of int-or-None.)
>
>
> A bientôt,
>
> Armin.
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+1 for IntFloatNoneButNotStrangeNans strategy