* feat(simplify): Allow context option If the options argument has a key 'context', it value is interpreted as a context specifying various (non-default) properties of operators. This context is propagated to all rules and all matching. Adds some initial tests that the context option affects the behavior of simplify appropriately. Not all can be activated until in a future commit we add the ability for the application of a rule to be contingent on aspects of the context. Note that the enhanced rule matching necessary to support rules constrained by non-default operator properties led to a couple of changes to the output of rationalize() as well. Since the new output seemed to better match what a person would typical write for the rationalized form, this commit changed the test rather than attempted to preserve the exact prior order of terms. * feat(simplifyCore): strip all parentheses Prior to this commit, simplifyCore stripped internal parentheses, but would leave top-level ones. But top-level parentheses don't carry any semantics, and no tests other than the ones that explicitly checked for the retention of top-level parentheses were affected by this change. Not making a special case for the top level also notably streamlined the code in simplifyCore. Adds tests for the new parenthesis-stripping behavior, as well as for other node types that were added earlier but which did not yet have simplifyCore tests. * refactor(simplifyCore): Strip any node marked as trivial in context This replaces special-case tests for unary + and parentheses, and paves the way for example for 'abs' being marked trivial in a putative positiveContext * refactor(simplify): Rename 'context' parameter to rules and document it. The new name is 'imposeContext' -- the motivation for the change is to distinguish the parameter for 'assuming', which will be added as a new parameter to control rule application based on context. * feat(simplify): Allow context-based conditions on rule application. Adds a new property of rules specified as objects: `assuming`. Its value should be a context, and every property specified in that context must match the incoming context, or else the rule will not be applied. Updates the constant floating rules to require their operators be commutative, as a test of the feature, and adds a unit test for this. * feat(simplify): annotate rules with underlying assumptions Also activates a number of tests of simplifications that should or should not occur in various contexts. To get all tests to pass, I could no longer find a rule ordering that worked in all cases, without the ability to mark an individual rule as applying repeatedly until just that rule stabilized. So this commit also adds that ability, and uses it to eliminate the tricky rule of expanding n1 + (n2 + n3)*(-1) to n1 + n2*(-1) + n3*(-1) late in the rule ordering, in favor of the more intuitive (complete) expansion of (n1 + n2)*(-1) to n1*(-1) + n2*(-1) early in the rule ordering, before constant folding and gathering of like terms. * feat(simplify): Add contexts for specific domains In particular, adds a `simplify.realContext` and a `simplify.positiveContext` which (attempt to) guarantee that no simplifications that change the value of the expression, on any real number or any positive real number, respectively, will occur. Adds multiple tests for these contexts, including verification that the simplification in either context does not change some example values of any of the expressions in any simplify test. This testing uncovered that it is unaryPlus that must be marked as trivial for simplifyCore to work properly, so that marking is added as well. * chore: Alter value consistency tests for browsers/older Node The problem was NaN != NaN in some JavaScripts but not others, so test for "both values NaN" explicitly before using deepEqual. * fix: Implement requested changes from review Added documentation about scope and context in top-level algebra functions page; made variable name less abbreviated; performed suggested refactoring. Co-authored-by: Jos de Jong <wjosdejong@gmail.com>
Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with different data types like numbers, big numbers, complex numbers, fractions, units, and matrices. Powerful and easy to use.
Features
- Supports numbers, big numbers, complex numbers, fractions, units, strings, arrays, and matrices.
- Is compatible with JavaScript's built-in Math library.
- Contains a flexible expression parser.
- Does symbolic computation.
- Comes with a large set of built-in functions and constants.
- Can be used as a command line application as well.
- Runs on any JavaScript engine.
- Is easily extensible.
- Open source.
Usage
Math.js can be used in both node.js and in the browser.
Install math.js using npm:
npm install mathjs
Or download mathjs via one of the CDN's listed on the downloads page:
https://mathjs.org/download.html
Math.js can be used similar to JavaScript's built-in Math library. Besides that, math.js can evaluate expressions and supports chained operations.
import {
atan2, chain, derivative, e, evaluate, log, pi, pow, round, sqrt
} from 'mathjs'
// functions and constants
round(e, 3) // 2.718
atan2(3, -3) / pi // 0.75
log(10000, 10) // 4
sqrt(-4) // 2i
pow([[-1, 2], [3, 1]], 2) // [[7, 0], [0, 7]]
derivative('x^2 + x', 'x') // 2 * x + 1
// expressions
evaluate('12 / (2.3 + 0.7)') // 4
evaluate('12.7 cm to inch') // 5 inch
evaluate('sin(45 deg) ^ 2') // 0.5
evaluate('9 / 3 + 2i') // 3 + 2i
evaluate('det([-1, 2; 3, 1])') // -7
// chaining
chain(3)
.add(4)
.multiply(2)
.done() // 14
See the Getting Started for a more detailed tutorial.
Browser support
Math.js works on any ES5 compatible JavaScript engine: node.js, Chrome, Firefox, Safari, Edge, and IE11.
Documentation
Build
First clone the project from github:
git clone git://github.com/josdejong/mathjs.git
cd mathjs
Install the project dependencies:
npm install
Then, the project can be build by executing the build script via npm:
npm run build
This will build ESM output, CommonJS output, and the bundle math.js from the source files and put them in the folder lib.
Develop
When developing new features for mathjs, it is good to be aware of the following background information.
Code
The code of mathjs is written in ES modules, and requires all files to have a real, relative path, meaning the files must have a *.js extension. Please configure adding file extensions on auto import in your IDE.
Architecture
What mathjs tries to achieve is to offer an environment where you can do calculations with mixed data types,
like multiplying a regular number with a Complex number or a BigNumber, and work with all of those in matrices.
Mathjs also allows to add a new data type, like say BigInt, with little effort.
The solution that mathjs uses has two main ingredients:
-
Typed functions. All functions are created using
typed-function. This makes it easier to (dynamically) create and extend a single function with new data types, automatically do type conversions on function inputs, etc. So, if you create function multiply for twonumbers, you can extend it with support for multiplying twoBigInts. If you define a conversion fromBigInttonumber, the typed-function will automatically allow you to multiply aBigIntwith anumber. -
Dependency injection. When we have a function
multiplywith support forBigInt, thanks to the dependency injection, other functions usingmultiplyunder the hood, likeprod, will automatically supportBigInttoo. This also works the other way around: if you don't need the heavyweightmultiply(which supports BigNumbers, matrices, etc), and you just need a plain and simple number support, you can use a lightweight implementation ofmultiplyjust for numbers, and inject that inprodand other functions.
At the lowest level, mathjs has immutable factory functions which create immutable functions. The core function math.create(...) creates a new instance having functions created from all passed factory functions. A mathjs instance is a collection of created functions. It contains a function like math.import to allow extending the instance with new functions, which can then be used in the expression parser.
Build scripts
The build script currently generates two types of output:
- any, generate entry points to create full versions of all functions
- number: generating and entry points to create lightweight functions just supporting
number
For each function, an object is generated containing the factory functions of all dependencies of the function. This allows to just load a specific set of functions, and not load or bundle any other functionality. So for example, to just create function add you can do math.create(addDependencies).
Test
To execute tests for the library, install the project dependencies once:
npm install
Then, the tests can be executed:
npm test
Additionally, the tests can be run on FireFox using headless mode:
npm run test:browser
To run the tests remotely on BrowserStack, first set the environment variables BROWSER_STACK_USERNAME and BROWSER_STACK_ACCESS_KEY with your username and access key and then execute:
npm run test:browserstack
You can separately run the code linter, though it is also executed with npm test:
npm run lint
To automatically fix linting issue, run:
npm run format
To test code coverage of the tests:
npm run coverage
To see the coverage results, open the generated report in your browser:
./coverage/lcov-report/index.html
Continuous integration testing
Continuous integration tests are run on Github Actions and BrowserStack every time a commit is pushed to github. Github Actions runs the tests for different versions of node.js, and BrowserStack runs the tests on all major browsers.
Thanks Github Actions and BrowserStack for the generous free hosting of this open source project!
License
Copyright (C) 2013-2022 Jos de Jong wjosdejong@gmail.com
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

