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Representing Constructible Numbers in Python

Build Status: Build Status

The constructible module provides exact representation of constructible numbers in Python.

Python 2 and Python 3 are supported.

The constructible numbers are the smallest field containing the rational numbers, where the square root of any non-negative constructible number is constructible as well. The non-negative constructible numbers are the lengths which can be constructed from the unit length using only a compass and a straightedge.

Usage

Usually the sqrt function is enough to work with constructible numbers:

>>> from constructible import sqrt
>>> x = sqrt(2) + sqrt(3)
>>> print(x)
((0 + 1 * sqrt(2)) + (1 + 0 * sqrt(2)) * sqrt((3 + 0 * sqrt(2))))
>>> y = x*x
>>> print(y)
((5 + 0 * sqrt(2)) + (0 + 2 * sqrt(2)) * sqrt((3 + 0 * sqrt(2))))
>>> z = y*y
>>> t = 10*y - z
>>> t == 1
True

Installation

To install from PYPI just type

pip install constructible

The library is a single pure python file, so it is also easy to install by hand.

Testing

There are some tests using unittest. Thanks to Travis-CI each push to github triggers a test: Build Status

Releasing on PYPI

The following steps are needed:

  • make sure .pypirc is up to date:

    [distutils]
index-servers =
  pypinew
  pypitest

[pypinew]
repository = https://upload.pypi.org/legacy/
username=xxx
password=xxx

[pypitest]
repository=https://test.pypi.org/legacy/
username=xxx
password=xxx

  • Update the version in setup.py

  • Tag the version in git:

    git tag 0.1 -m "Adds a tag so that we can put this on PyPI."
git push --tags origin

  • Test release with:

    python setup.py sdist upload -r pypitest

  • Productive release with:

    python setup.py sdist upload -r pypinew

Changelog

  • 2016-05-23 V0.1 Initial Release
  • 2016-09-30 V0.2 Fixing Issue 1 and added Tests
  • 2016-10-03 V0.3 Fixing Issue 2
  • 2016-10-23 V0.4 Added __hash__ and __float__, speed optimizations
  • 2020-07-08 V0.5 New hash function and improvements by Arsenii A.

Aknowledgements

Thanks to Anders Kaseorg whose implementation of constructible numbers in Haskell provided inspiration and in particular the algorithm for taking square roots in quadratic extension fields.