com-nospam@ccraig.org (Christopher A. Craig) writes:

"Tim Peters" writes:

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[Christopher A. Craig, playing with modifying the meaning of division]

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... While doing this I was thinking that I would change true_division on ints and floats to return a rational and change the rational code to return a long if the denominator is 1. This works great, except that if future division is off then rationals can suddenly become longs and do not automatically cast back. This makes it virtually impossible to guarantee a correct result to nearly any rational computation that involves a division.

So I wanted to know if there is some way to detect, at the object level, if the CO_FUTURE_DIVISION feature is active.

I'm unclear on what you're asking. In case it helps, note this section in __future__.py:

Hmm, I thought I was being too verbose, I guess I was being too unclear. I have a rational module (in C) which I am trying to patch to be an object satisfying PEP-239. The problem is that I would like to have an rational cast back to a integer iff (1) the denominator is 1 and (2) future division is active.

If I don't check (2) then I get the situation that if future division is inactive then `(rational('1/3')*3)/5` would yield 0 instead of 1/5. This makes rationals pretty much useless unless future division is active.

What I would like to do is have a function that can check to see if the CO_FUTURE_DIVISION flag is set and if it is and the denominator is 1 then return the numerator, else return the rational.

I have a strong suspicion that this can't be done, in which case I just won't do the cast back automatically.

Does this: int is_future_div(void) { PyCompilerFlags cf; PyEval_MergeCompilerFlags(&cf); return cf.cf_flags & CO_FUTURE_DIVISION; } work? You'll need to change this when future division becomes the default, but I think it'll work today. This is a murky dark corner of the interpreter, though -- so don't blame me when it breaks! Cheers, M. -- >> REVIEW OF THE YEAR, 2000 << It was shit. Give us another one. -- NTK Know, 2000-12-29, http://www.ntk.net/