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Re: Generarl programming question.

References <dcb7fd6b-3a96-47e8-91f6-49b21f7bf605@googlegroups.com> <mailman.222.1428765309.12925.python-list@python.org> <1f4ab217-ed8e-4d8c-ba61-907465a4839a@googlegroups.com>
Date 2015-04-12 01:28 +1000
Subject Re: Generarl programming question.
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.223.1428766115.12925.python-list@python.org> (permalink)

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On Sun, Apr 12, 2015 at 1:22 AM,  <jonas.thornvall@gmail.com> wrote:
> Thanks i was worried, i try to make a generic base choice algorithm that should work for anybase, and i just realised that the bignumb add would need to call the bignumb subtraction and viceversa. I thought there may be instances but i was not sure.
>
> But I have a feeling the code will be hard to debug.

The thing to watch out for is unbounded recursion, where they might
call each other forever. But you could easily define your two
functions to fall back to the other like this:

def add(x, y):
    if is_negative(y): return subtract(x, -y)
    # implement addition with known-positive y

def subtract(x, y):
    if is_negative(y): return add(x, -y)
    # implement subtraction with known-positive y

There's no problem here, and no possible conflict. (I don't know how
it'd actually help, implementing it like this, but it's certainly
legal.)

ChrisA

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Thread

Generarl programming question. jonas.thornvall@gmail.com - 2015-04-11 08:00 -0700
  Re: Generarl programming question. Chris Angelico <rosuav@gmail.com> - 2015-04-12 01:15 +1000
    Re: Generarl programming question. jonas.thornvall@gmail.com - 2015-04-11 08:22 -0700
      Re: Generarl programming question. Chris Angelico <rosuav@gmail.com> - 2015-04-12 01:28 +1000
    Re: Generarl programming question. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-11 18:23 +0200
      Re: Generarl programming question. Terry Reedy <tjreedy@udel.edu> - 2015-04-11 14:47 -0400
        Re: Generarl programming question. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-11 21:19 +0200
          Re: Generarl programming question. Terry Reedy <tjreedy@udel.edu> - 2015-04-11 17:12 -0400
            Re: Generarl programming question. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-12 00:05 +0200
              Re: Generarl programming question. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-12 15:04 +1000
  Re: Generarl programming question. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-12 01:25 +1000
    Re: Generarl programming question. jonas.thornvall@gmail.com - 2015-04-11 08:36 -0700

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