math-float64-flipsign

Flipsign

Returns a double-precision floating-point number with the magnitude of x and the sign of x*y.

Installation

$ npm install math-float64-flipsign

Usage

var flipsign = require( 'math-float64-flipsign' );

flipsign( x, y )

Returns a double-precision floating-point number with the magnitude of x and the sign of x*y; i.e., only return -x when y is a negative number.

var z = flipsign( -3.14, 10 );
// returns -3.14
 
z = flipsign( -3.14, -1 );
// returns 3.14
 
z = flipsign( 1, -0 );
// returns -1
 
z = flipsign( -3.14, -0 );
// returns 3.14
 
z = flipsign( -0, 1 );
// returns -0
 
z = flipsign( 0, -1 );
// returns -0

Notes

• According to the IEEE754 standard, a NaN has a biased exponent equal to 2047, a significand greater than 0, and a sign bit equal to either 1 or 0. In which case, NaN may not correspond to just one but many binary representations. Accordingly, care should be taken to ensure that y is not NaN, else behavior may be indeterminate.

Examples

var flipsign = require( 'math-float64-flipsign' );
 
var x;
var y;
var z;
var i;
 
// Generate random double-precision floating-point numbers `x` and `y` and flip the sign of `x` only if `y` is negative...
for ( i = 0; i < 100; i++ ) {
    x = Math.random()*100 - 50;
    y = Math.random()*10 - 5;
    z = flipsign( x, y );
    console.log( 'x: %d, y: %d => %d', x, y, z );
}

To run the example code from the top-level application directory,

$ node ./examples/index.js

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Tests

Unit

This repository uses tape for unit tests. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

Browser Support

This repository uses Testling for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:

$ make test-browsers

To view the tests in a local web browser,

$ make view-browser-tests

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License

MIT license.

Copyright

Copyright © 2016. The Compute.io Authors.