107 lines
3.2 KiB
Markdown
107 lines
3.2 KiB
Markdown
Equation [](https://travis-ci.org/mdibaiee/Equation)
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========
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Solve math expressions or create equations for repeated and complex Math tasks.
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To use in browser, download [`equation.min.js`](https://raw.githubusercontent.com/mdibaiee/Equation/master/equation.min.js).
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_A similar library I wrote in Haskell is also available [mathexpr](https://github.com/mdibaiee/mathexpr)_
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Install using npm:
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```
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npm install equations
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```
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#### Examples:
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```javascript
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//import
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const Equation = require('equations').default
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// solve
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console.log(Equation.solve('4 * lg(4) ^ 3')); // 32
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// equation
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let sphereArea = Equation.equation('4 * PI * r^2');
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console.log(sphereArea(5)); // 314.1592653589793
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let test = Equation.equation('2x + 6y');
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console.log(test(4, 3)).to.equal(8 + 18);
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```
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You can also register your own operators and constants.
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```javascript
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// these options are explained in [`operators.js`](https://github.com/mdibaiee/Equation/blob/master/lib/operators.js).
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Equation.registerOperator('$', {
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fn: a => 1/a,
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format: '10',
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precedence: 2
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});
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Equation.solve('$2'); // 0.5
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Equation.solve('$5'); // 0.2
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Equation.registerConstant('N', () => {
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return Math.random() * 10 + 10
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});
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Equation.solve('N'); // a number between 10 and 20
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// Complex operators
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Equation.solve('sigma(0, 5, 2@ + 5)'); // 60
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```
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For a list of operators and constants see [`operators.js`](https://github.com/mdibaiee/Equation/blob/master/lib/operators.js) and [`constants.js`](https://github.com/mdibaiee/Equation/blob/master/lib/constants.js).
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API
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===
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#### solve(expression: String)
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Takes a math expression and evaluates it, returning the result.
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#### equation(expression: String)
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Takes a math expression containing variables, returning a function which
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replaces the variables with given arguments, and solves the expression.
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#### registerOperator(key: String, options: Object)
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Registers a new operator.
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Options:
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##### fn
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The function which is run on arguments and returns the result
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##### format
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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.
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For example `+` has the format `010` and factorial has `01`.
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##### precedence
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Specifies the precedence of operator. The less the value, the higher the precedence, resulting in sooner execution.
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#### registerConstant(key: String, value: Function/Number)
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Registers a new constant. value can be a function (takes no arguments), or a constant number.
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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`.
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Contributing
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============
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The code is commented and I hope you don't have a hard time contributing,
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anyway, some tips about contributing:
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The source code is in `lib` directory and is then transpiled into `dist`.
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#####Grunt Tasks
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######default
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Transpiles `lib` to `dist`
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######build
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Transpiles, browserifies, uglifies
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######eslint
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Runs ESLint on `lib` and `tests`
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######test
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Runs the tests
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---
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Please make sure to run `grunt eslint` before commiting.
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If you're adding something new, please add a test, too.
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