[Python-Dev] Octal literals (original) (raw)

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 PyArgParseTuple, 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 PyArgParseTuple. 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.

Regards, Bengt Richter

More information about the Python-Dev mailing list