Loris is a term rewriting and computer algebra system based on pattern matching algorithms developed by Besik Dundua, Temur Kutsia, and Mircea Marin. (See below.) To my knowledge, this is the first and only implementation of these algorithms.
This repository is for lorislib, the library that implements almost all of Loris. There is also a front end: Loris-CLI. When I make a repository for the project as a whole that brings in lorislib and loris_cli as git submodules, it will be located here: https://github.com/rljacobson/loris.
You will need Loris-CLI. Follow the build instructions there.
Loris uses syntax similar to Mathematica:
f[x_] := 1 + x^2You can think of Loris as an implementation of Wolfram Language. Only a handful of built-ins and predefined
functions exist so far. Expect only basic arithmetic functions and system-related built-ins to work. However, it is
nearing the point where it has enough built-ins to implement a powerful CAS in its own language. Source files for
this implementation will accrue in lib/.
Another major limitation is that the matcher only has linear matching implemented so far, meaning that a variable can
only appear once on the LHS of a function definition. To get around this limitation, you can include a
Condition in your definition: f[x_, y_] := expr /; condition. Here is a simplification rule (using UpSet)
that employs this workaround:
a_*x_ + b_*y_ ^:= (a + b)*x /; And[SameQ[x, y], NumberQ[a], NumberQ[b]]When I implement Algorithm
Loris started as an implementation of the pattern matching algorithms described in the paper:
Besik Dundua, Temur Kutsia, and Mircea Marin, Variadic equational matching in associative and commutative theories, Journal of Symbolic Computation, vol 106, 2021, p. 78-109
We implement algorithms LM (Linear Matching) and LM${\text{S}}$ (Linear Matching with Strict associativity) as described in the paper with a minor modification to LM to make it finitary. The algorithm relies on repeated application of transformation rules to "match equations." The algorithm is described in doc/Algorithm.md. The transformation rules are listed in doc/TransformationRules.md and implemented in the files in src/matching/. The algorithm $M{\text{MMA}}$, which captures the semantics of Wolfram Mathematica's matching behavior, is not implemented, but I would like to implement it in the future.
Algorithms
Copyright (C) 2022 Robert Jacobson. This software is distributed under the 2-Clause BSD License.
The source code of the permutation-generator crate by Thomas
Villa has been included in its entirety in lorislib/src/matching/permutation_generator. The permutaton-generator
crate is distributed under the MIT license.
Feel free to contribute. I am happy to take PRs. Unfortunately, I generally have so much happening in my life that I cannot offer support for my software projects on GitHub. Feel free to fork the project, though.
The Slow Loris is at risk of extinction due to habitat loss and the illegal wildlife trade. There is demand for lorises for use in traditional medicine and as pets.