frac

What is frac?

The frac npm package is designed to compute the fractional part of a number, effectively separating the integer part from the decimal part of a number. This can be particularly useful in mathematical, engineering, or scientific applications where precision with decimal numbers is required.

What are frac's main functionalities?

Fractional Part Extraction

This feature allows you to extract the fractional part of a number. The function returns an array where the first element is the decimal fraction, the second is the numerator, the third is the denominator, and the fourth is the sign.

const frac = require('frac');

let result = frac(4.567);
// result will be [0.567, 567, 1000, 3] representing the fraction, numerator, denominator, and sign.

Handling Negative Numbers

The package can also handle negative numbers, returning the fractional part along with the sign, which can be useful for applications that need to distinguish between positive and negative fractions.

const frac = require('frac');

let result = frac(-2.345);
// result will be [-0.345, 345, 1000, -1] indicating the fraction, numerator, denominator, and sign for negative numbers.

Other packages similar to frac

mathjs

mathjs is a comprehensive math library for JavaScript and Node.js. It offers a wide range of functionalities including arithmetic, algebraic operations, and more. Compared to frac, mathjs is much more extensive, providing functionalities far beyond fractional part extraction.

fraction.js

fraction.js is focused on fraction operations, allowing for creation, manipulation, and conversion of fractions. While frac specifically extracts the fractional part of numbers, fraction.js provides a broader set of tools for working with fractions as first-class objects.

README

frac

Rational approximation to a floating point number with bounded denominator.

Uses the Mediant Method.

This module also provides an implementation of the continued fraction method as described by Aberth in "A method for exact computation with rational numbers". The algorithm is used in SheetJS Libraries to replicate fraction formats.

Installation

JS

With npm:

$ npm install frac

In the browser:

<script src="frac.js"></script>

The script will manipulate module.exports if available (e.g. in a CommonJS require context). This is not always desirable. To prevent the behavior, define DO_NOT_EXPORT_FRAC

Python

From PyPI:

$ pip install frac

Usage

In all cases, the relevant function takes 3 arguments:

• x the number we wish to approximate
• D the maximum denominator
• mixed if true, return a mixed fraction; if false, improper

The return value is an array of the form [quot, num, den] where quot==0 for improper fractions. quot <= x for mixed fractions, which may lead to some unexpected results when rendering negative numbers.

JS

The exported frac function implements the Mediant method.

frac.cont implements the Aberth algorithm

For example:

> // var frac = require('frac'); // uncomment this line if in node
> frac(1.3, 9);              // [  0,  9, 7 ] //  1.3 ~       9/7
> frac(1.3, 9, true);        // [  1,  2, 7 ] //  1.3 ~  1 +  2/7
> frac(-1.3, 9);             // [  0, -9, 7 ] // -1.3 ~      -9/7
> frac(-1.3, 9, true);       // [ -2,  5, 7 ] // -1.3 ~ -2 +  5/7

> frac.cont(1.3, 9);         // [  0,  4, 3 ] //  1.3 ~       4/3
> frac.cont(1.3, 9, true);   // [  1,  1, 3 ] //  1.3 ~  1 +  1/3
> frac.cont(-1.3, 9);        // [  0, -4, 3 ] // -1.3 ~      -4/3
> frac.cont(-1.3, 9, true);  // [ -2,  2, 3 ] // -1.3 ~ -2 +  2/3

Python

frac.med implements Mediant method.

frac.cont implements Aberth algorithm.

For example:

>>> import frac
>>> frac.med(1.3, 9)         ## [  0,  9, 7 ] ##  1.3 ~       9/7
>>> frac.med(1.3, 9, True)   ## [  1,  2, 7 ] ##  1.3 ~  1 +  2/7
>>> frac.med(-1.3, 9)        ## [  0, -9, 7 ] ## -1.3 ~      -9/7
>>> frac.med(-1.3, 9, True)  ## [ -2,  5, 7 ] ## -1.3 ~ -2 +  5/7

>>> frac.cont(1.3, 9)        ## [  0,  4, 3 ] ##  1.3 ~       4/3
>>> frac.cont(1.3, 9, True)  ## [  1,  1, 3 ] ##  1.3 ~  1 +  1/3
>>> frac.cont(-1.3, 9)       ## [  0, -4, 3 ] ## -1.3 ~      -4/3
>>> frac.cont(-1.3, 9, True) ## [ -2,  2, 3 ] ## -1.3 ~ -2 +  2/3

Testing

The test TSV baselines in the test_files directory have four columns:

• Column A contains the raw values
• Column B format "Up to one digit (1/4)" (denominator = 9)
• Column C format "Up to two digits (21/25)" (denominator = 99)
• Column D format "Up to three digits (312/943)" (denominator = 999)

make test will run the node-based tests.

make pytest will run the python tests against the system Python version.

make pypytest will run the python tests against pypy if installed

License

Please consult the attached LICENSE file for details. All rights not explicitly granted by the Apache 2.0 License are reserved by the Original Author.

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