[Python-Dev] Octal literals

Bengt Richter bokr at oz.net
Sat Feb 4 00:08:39 CET 2006

On Fri, 03 Feb 2006 19:56:20 +0100, =?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?= <martin at v.loewis.de> wrote:

>Bengt Richter wrote:
>> If you are looking at them in C code receiving them as args in a call,
>> "treat them the same" would have to mean provide code to coerce long->int
>> or reject it with an exception, IWT.
>The typical way of processing incoming ints in C is through
>PyArg_ParseTuple, which already has the code to coerce long->int
>(which in turn may raise an exception for a range violation).
>So for typical C code, 0x80000004 is a perfect bit mask in Python 2.4.
Ok, I'll take your word that 'k' coercion takes no significant time for longs vs ints.
I thought there might be a case in a hot loop where it could make a difference.
I confess not having done a C extension since I wrote one to access RDTSC quite some time ago.

>> It's not a matter of "buggy" if you are trying to optimize.
>> (I am aware of premature optimization issues, and IMO "strange"
>> is in the eye of the beholder. What syntax would you suggest?
>The question is: what is the problem you are trying to solve?
>If it is "bit masks", then consider the problem solved already.
Well, I was visualizing having a homogeneous bunch of bit mask
definitions all as int type if they could fit. I can't express
them all in hex as literals without some processing. That got me started ;-)
Not that some one-time processing at module import time is a big deal.
Just that it struck me as a wart not to be able to do it without processing,
even if constant folding is on the way.

>>>Same goes for code that says it takes a 32-bit bitfield argument but  
>>>won't accept 0x80000000.
>> If the bitfield is signed, it can't, unless you are glossing over
>> an assumed coercion rule.
>Just have a look at the 'k' specifier in PyArg_ParseTuple.
Ok, well that's the provision for the coercion then.
BTW, is long mandatory for all implementations? Is there a doc that
defines minimum features for a conforming Python implementation?
E.g., IIRC Scheme has a list naming what's optional and not.

Bengt Richter

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