From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 23 Nov 2019 23:39:21 +0000 (+0000)
Subject: catacomb/__init__.py: Prepare rational classes for upcoming changes.
X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb-python/commitdiff_plain/e127f835319e4b5e6dcdc2f0ed9a111a47fcecdf?hp=e127f835319e4b5e6dcdc2f0ed9a111a47fcecdf

catacomb/__init__.py: Prepare rational classes for upcoming changes.

In the near future, we won't be able to guarantee that all rings allow
implicit conversions of (integer) 0 and 1 to the additive and
multiplicative ring identities, so:

  * define `ZERO' and `ONE' class attributes on the concrete classes to
    hold the respective ring identities;

  * make the `_split_rat' function into a private method of the
    `BaseRat' class and adjust callers to match;

  * compare against `ZERO' to detect an exact element of the base ring;
    and

  * return `ONE' as the implicit denominator for a base-ring element or
    foreign object to be converted.

No functional change.
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