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244 lines
7.4 KiB
244 lines
7.4 KiB
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An arbitrary-precision Decimal type for JavaScript.
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[](https://www.npmjs.com/package/decimal.js)
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[](https://www.npmjs.com/package/decimal.js)
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[](https://travis-ci.org/MikeMcl/decimal.js)
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[](https://cdnjs.com/libraries/decimal.js)
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<br>
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## Features
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- Integers and floats
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- Simple but full-featured API
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- Replicates many of the methods of JavaScript's `Number.prototype` and `Math` objects
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- Also handles hexadecimal, binary and octal values
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- Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal
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- No dependencies
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- Wide platform compatibility: uses JavaScript 1.5 (ECMAScript 3) features only
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- Comprehensive [documentation](https://mikemcl.github.io/decimal.js/) and test set
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- Includes a TypeScript declaration file: *decimal.d.ts*
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The library is similar to [bignumber.js](https://github.com/MikeMcl/bignumber.js/), but here
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precision is specified in terms of significant digits rather than decimal places, and all
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calculations are rounded to the precision (similar to Python's decimal module) rather than just
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those involving division.
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This library also adds the trigonometric functions, among others, and supports non-integer powers,
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which makes it a significantly larger library than *bignumber.js* and the even smaller
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[big.js](https://github.com/MikeMcl/big.js/).
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For a lighter version of this library without the trigonometric functions see
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[decimal.js-light](https://github.com/MikeMcl/decimal.js-light/).
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## Load
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The library is the single JavaScript file *decimal.js* or ES module *decimal.mjs*.
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Browser:
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```html
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<script src='path/to/decimal.js'></script>
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```
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or
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```html
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<script type="module">
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import Decimal from './path/to/decimal.mjs';
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...
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</script>
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```
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[Node.js](https://nodejs.org):
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```bash
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npm install decimal.js
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```
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```js
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var Decimal = require('decimal.js');
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```
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or
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```js
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import Decimal from 'decimal.js';
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```
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or
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```js
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import {Decimal} from 'decimal.js';
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```
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## Use
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*In all examples below, `var`, semicolons and `toString` calls are not shown.
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If a commented-out value is in quotes it means `toString` has been called on the preceding expression.*
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The library exports a single function object, `Decimal`, the constructor of Decimal instances.
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It accepts a value of type number, string or Decimal.
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```js
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x = new Decimal(123.4567)
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y = new Decimal('123456.7e-3')
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z = new Decimal(x)
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x.equals(y) && y.equals(z) && x.equals(z) // true
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```
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A value can also be in binary, hexadecimal or octal if the appropriate prefix is included.
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```js
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x = new Decimal('0xff.f') // '255.9375'
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y = new Decimal('0b10101100') // '172'
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z = x.plus(y) // '427.9375'
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z.toBinary() // '0b110101011.1111'
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z.toBinary(13) // '0b1.101010111111p+8'
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```
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Using binary exponential notation to create a Decimal with the value of `Number.MAX_VALUE`:
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```js
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x = new Decimal('0b1.1111111111111111111111111111111111111111111111111111p+1023')
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```
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A Decimal is immutable in the sense that it is not changed by its methods.
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```js
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0.3 - 0.1 // 0.19999999999999998
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x = new Decimal(0.3)
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x.minus(0.1) // '0.2'
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x // '0.3'
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```
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The methods that return a Decimal can be chained.
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```js
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x.dividedBy(y).plus(z).times(9).floor()
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x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4_444_562_598.111772').ceil()
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```
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Many method names have a shorter alias.
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```js
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x.squareRoot().dividedBy(y).toPower(3).equals(x.sqrt().div(y).pow(3)) // true
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x.cmp(y.mod(z).neg()) == 1 && x.comparedTo(y.modulo(z).negated()) == 1 // true
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```
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Like JavaScript's Number type, there are `toExponential`, `toFixed` and `toPrecision` methods,
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```js
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x = new Decimal(255.5)
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x.toExponential(5) // '2.55500e+2'
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x.toFixed(5) // '255.50000'
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x.toPrecision(5) // '255.50'
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```
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and almost all of the methods of JavaScript's Math object are also replicated.
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```js
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Decimal.sqrt('6.98372465832e+9823') // '8.3568682281821340204e+4911'
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Decimal.pow(2, 0.0979843) // '1.0702770511687781839'
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```
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There are `isNaN` and `isFinite` methods, as `NaN` and `Infinity` are valid `Decimal` values,
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```js
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x = new Decimal(NaN) // 'NaN'
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y = new Decimal(Infinity) // 'Infinity'
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x.isNaN() && !y.isNaN() && !x.isFinite() && !y.isFinite() // true
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```
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and a `toFraction` method with an optional *maximum denominator* argument
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```js
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z = new Decimal(355)
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pi = z.dividedBy(113) // '3.1415929204'
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pi.toFraction() // [ '7853982301', '2500000000' ]
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pi.toFraction(1000) // [ '355', '113' ]
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```
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All calculations are rounded according to the number of significant digits and rounding mode specified
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by the `precision` and `rounding` properties of the Decimal constructor.
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For advanced usage, multiple Decimal constructors can be created, each with their own independent
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configuration which applies to all Decimal numbers created from it.
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```js
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// Set the precision and rounding of the default Decimal constructor
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Decimal.set({ precision: 5, rounding: 4 })
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// Create another Decimal constructor, optionally passing in a configuration object
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Decimal9 = Decimal.clone({ precision: 9, rounding: 1 })
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x = new Decimal(5)
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y = new Decimal9(5)
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x.div(3) // '1.6667'
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y.div(3) // '1.66666666'
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```
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The value of a Decimal is stored in a floating point format in terms of its digits, exponent and sign.
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```js
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x = new Decimal(-12345.67);
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x.d // [ 12345, 6700000 ] digits (base 10000000)
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x.e // 4 exponent (base 10)
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x.s // -1 sign
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```
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For further information see the [API](http://mikemcl.github.io/decimal.js/) reference in the *doc* directory.
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## Test
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The library can be tested using Node.js or a browser.
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The *test* directory contains the file *test.js* which runs all the tests when executed by Node,
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and the file *test.html* which runs all the tests when opened in a browser.
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To run all the tests, from a command-line at the root directory using npm
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```bash
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npm test
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```
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or at the *test* directory using Node
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```bash
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node test
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```
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Each separate test module can also be executed individually, for example, at the *test/modules* directory
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```bash
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node toFraction
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```
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## Minify
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The minified version of *decimal.js* and its associated source map found in this repository was created with
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[uglify-js](https://github.com/mishoo/UglifyJS) using
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```bash
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npm install uglify-js -g
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uglifyjs decimal.js --source-map url=decimal.min.js.map --compress --mangle --output decimal.min.js
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```
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The minified version of *decimal.mjs* and its associated source map found in this repository was created with
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[terser](https://github.com/terser/terser) using
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```bash
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npm install terser -g
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terser decimal.mjs --source-map url=decimal.min.mjs.map -c -m --toplevel -o decimal.min.mjs
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```
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```js
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import Decimal from './decimal.min.mjs';
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```
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## Licence
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MIT.
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See *LICENCE.md*
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