Equation

Solve math expressions or create equations for repeated and complex Math tasks.

To use in browser, download equation.min.js.

A similar library I wrote in Haskell is also available mathexpr

Install using npm:

npm install equations

Examples:

//import

const Equation = require('equations').default

// solve
console.log(Equation.solve('4 * lg(4) ^ 3')); // 32

// equation
let sphereArea = Equation.equation('4 * PI * r^2');
console.log(sphereArea(5)); // 314.1592653589793

let test = Equation.equation('2x + 6y');
console.log(test(4, 3)).to.equal(8 + 18);

You can also register your own operators and constants.

// these options are explained in [`operators.js`](https://github.com/mdibaiee/Equation/blob/master/lib/operators.js).
Equation.registerOperator('$', {
  fn: a => 1/a,
  format: '10',
  precedence: 2
});

Equation.solve('$2'); // 0.5
Equation.solve('$5'); // 0.2

Equation.registerConstant('N', () => {
  return Math.random() * 10 + 10
});

Equation.solve('N'); // a number between 10 and 20

// Complex operators
Equation.solve('sigma(0, 5, 2@ + 5)'); // 60

For a list of operators and constants see operators.js and constants.js.

API

solve(expression: String)

Takes a math expression and evaluates it, returning the result.

equation(expression: String)

Takes a math expression containing variables, returning a function which replaces the variables with given arguments, and solves the expression.

registerOperator(key: String, options: Object)

Registers a new operator.

Options:

fn

The function which is run on arguments and returns the result

format

The format which specifies how arguments are placed relative to operator, this is a string in which 1 represents the operator and zeroes represent arguments.

For example + has the format 010 and factorial has 01.

precedence

Specifies the precedence of operator. The less the value, the higher the precedence, resulting in sooner execution.

registerConstant(key: String, value: Function/Number)

Registers a new constant. value can be a function (takes no arguments), or a constant number.

That's right, we have named these constants, but they actually can change, that's why we can use functions to define them. An example is the RAND constant which calls Math.random.

Contributing

The code is commented and I hope you don't have a hard time contributing, anyway, some tips about contributing:

The source code is in lib directory and is then transpiled into dist.

#####Grunt Tasks ######default Transpiles lib to dist ######build Transpiles, browserifies, uglifies ######eslint Runs ESLint on lib and tests ######test Runs the tests

---

Please make sure to run grunt eslint before commiting.

If you're adding something new, please add a test, too.