On Wed, Mar 26, 2008 at 9:18 AM, Alexander Belopolsky
<[EMAIL PROTECTED]> wrote:
>
> On Tue, Mar 25, 2008 at 5:06 PM, Adam Olsen <[EMAIL PROTECTED]> wrote:
> > On Tue, Mar 25, 2008 at 2:43 PM, Alexander Belopolsky
> >
> > <[EMAIL PROTECTED]> wrote:
> >
> > > On Tue, Mar 25, 2008 at 4:26 PM, Adam Olsen <[EMAIL PROTECTED]> wrote:
> >
> > > > It does not even have to be a frozenset. A set works just as well,
> > > > never modified by the produced bytecode.
> > >
> > > With the current implementation, precomputed constants must be
> > > hashable because the compiler uses a dictionary lookup in order to
> > > eliminate duplicates. This is of course just an implementation
> > > detail, but it would actually be hard to work around it.
> >
> > Only builtin types with literal syntax may be deemed "constant"
> > anyway. I fail to see how that's relevant to my frozenset vs set
> > comment.
>
> I realized that right after I hit the "send" button, so my comment
> about optimizing
> frozenset({...}) was wrong. With respect to frozenset vs set comment,
> I understand
> your proposal as transforming current
>
> >>> dis(lambda: i in {1,2,3})
> 1 0 LOAD_GLOBAL 0 (i)
>
> 3 LOAD_CONST 0 (1)
> 6 LOAD_CONST 1 (2)
> 9 LOAD_CONST 2 (3)
> 12 BUILD_SET 3
> 15 COMPARE_OP 6 (in)
> 18 RETURN_VALUE
>
>
> to
>
> 1 0 LOAD_GLOBAL 0 (i)
> 3 LOAD_CONST 3 ({1, 2, 3})
> 6 COMPARE_OP 6 (in)
> 9 RETURN_VALUE
>
> This will not work because {1, 2, 3} is not hashable, but it should be
> possible to do
>
> 1 0 LOAD_GLOBAL 0 (i)
> 3 LOAD_CONST 3 (frozenset({1, 2, 3}))
> 6 COMPARE_OP 6 (in)
> 9 RETURN_VALUE
Ahh, I see! It's "safe" to use a set, but it internally gets stuck in
a dict to intern it, which a set doesn't allow. Fixable, but
annoying.
> On the other hand, our dialog is increasingly off-topic. My original
> question was whether or not it will be a good idea to unify how set
> and dict literals are processed. Please comment on the following
> options:
>
> 1. Do nothing: dicts are built incrementally, and sets in batch.
> 2. Implement batch processing for dict literals.
> 3. Implement incremental processing for sets.
>
> My order of preference is 2, 1, 3.
IMHO, just go ahead with 2.
--
Adam Olsen, aka Rhamphoryncus
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