Groups > comp.lang.python > #101966

Re: How to simulate C style integer division?

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From	Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de>
Newsgroups	comp.lang.python
Subject	Re: How to simulate C style integer division?
Date	Thu, 21 Jan 2016 15:22:12 +0100
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On 1/21/2016 15:00, Jussi Piitulainen wrote:
> Steven D'Aprano writes:
>
>> So my guess is that the fastest, and certainly the most obvious, way
>> to get the same integer division behaviour as C99 would be:
>>
>> def intdiv(a, b):
>>      # C99 style integer division with truncation towards zero.
>>      n = a//b
>>      if (a < 0) != (b < 0):
>>          n += 1
>>      return n
>
> You should only increment if there is a (non-zero) remainder.
>

Right. Merging Steven's suggestion and fractions.Fraction.__trunc__ 
implementation I think the right answer may be:

def intdiv2(a,b):
     # C99 style integer division with truncation towards zero.
     if (a < 0) != (b < 0):
         return -(-a // b)
     else:
         return a // b

Cheers,
Wolfgang


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Thread

Re: How to simulate C style integer division? Ben Finney <ben+python@benfinney.id.au> - 2016-01-21 20:11 +1100
  Re: How to simulate C style integer division? Paul Rubin <no.email@nospam.invalid> - 2016-01-21 01:43 -0800
    Re: How to simulate C style integer division? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-01-21 11:58 +0200
  Re: How to simulate C style integer division? Steven D'Aprano <steve@pearwood.info> - 2016-01-21 23:42 +1100
    Re: How to simulate C style integer division? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-01-21 16:00 +0200
      Re: How to simulate C style integer division? Marko Rauhamaa <marko@pacujo.net> - 2016-01-21 16:31 +0200
        Re: How to simulate C style integer division? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-01-21 16:48 +0200
        Re: How to simulate C style integer division? Random832 <random832@fastmail.com> - 2016-01-21 14:52 -0500
          Re: How to simulate C style integer division? Marko Rauhamaa <marko@pacujo.net> - 2016-01-21 23:17 +0200
            Re: How to simulate C style integer division? Matt Wheeler <m@funkyhat.org> - 2016-01-22 00:51 +0000
      Re: How to simulate C style integer division? Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de> - 2016-01-21 15:22 +0100

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