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math-float32-normalize

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Readme

Normalize

$NPM version$ $Build Status$ $Coverage Status$ $Dependencies$

Returns a normal number y and exponent exp satisfying x = y * 2^exp.

Installation

$ npm install math-float32-normalize

Usage

var normalize = require( 'math-float32-normalize' );

normalize( x )

Returns a normal number y and exponent exp satisfying x = y * 2^exp.

var toFloat32 = require( 'float64-to-float32' );

var out = normalize( toFloat32( 1.401e-45 ) );
// returns [ 1.1754943508222875e-38, -23 ]

The first element of the returned array corresponds to y and the second to exp.

var pow = require( 'math-power' );

var y = out[ 0 ];
var exp = out[ 1 ];

var bool = ( y*pow(2,exp) === toFloat32(1.401e-45) );
// returns true

The function expects a finite, non-zero single-precision floating-point number x. If x == 0,

var out = normalize( 0 );
// returns [ 0, 0 ];

If x is either positive or negative infinity or NaN,

var pinf = require( 'const-pinf-float32' );
var ninf = require( 'const-ninf-float32' );

var out = normalize( pinf );
// returns [ pinf, 0 ]

out = normalize( ninf );
// returns [ ninf, 0 ]

out = normalize( NaN );
// returns [ NaN, 0 ]

Notes

While the function accepts higher precision floating-point numbers, beware that providing such numbers can be a source of subtle bugs as the relation x = y * 2^exp may not hold.

Examples

var round = require( 'math-round' );
var pow = require( 'math-power' );
var toFloat32 = require( 'float64-to-float32' );
var normalize = require( 'math-float32-normalize' );

var frac;
var exp;
var x;
var v;
var i;

// Generate denormalized single-precision floating-point numbers and then normalize them...
for ( i = 0; i < 100; i++ ) {
    frac = Math.random() * 10;
    exp = 38 + round( Math.random()*6 );
    x = frac * pow( 10, -exp );
    x = toFloat32( x );
    v = normalize( x );
    console.log( '%d = %d * 2^%d = %d', x, v[0], v[1], v[0]*pow(2,v[1]) );
}

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

$ node ./examples/index.js

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

License

MIT license.

math-float32-normalize