From Bits

Creates a double-precision floating-point number from a literal bit representation.

Installation

$ npm install math-float64-from-bits

Usage

var fromBits = require( 'math-float64-from-bits' );

fromBits( bstr )

Creates a double-precision floating-point number from a literal bit representation.

var bstr = '0100000000010000000000000000000000000000000000000000000000000000';
var val = fromBits( bstr );
// returns 4
 
bstr = '0100000000001001001000011111101101010100010001000010110100011000';
val = fromBits( bstr );
// returns 3.141592653589793
 
bstr = '1111111111100001110011001111001110000101111010111100100010100000';
val = fromBits( bstr );
// returns -1e308

The function handles subnormals.

bstr = '1000000000000000000000000000000000000000000000000001100011010011';
val = fromBits( bstr );
// returns -3.14e-320
 
bstr = '0000000000000000000000000000000000000000000000000000000000000001';
val = fromBits( bstr );
// returns 5e-324

The function handles special values.

bstr = '0000000000000000000000000000000000000000000000000000000000000000';
val = fromBits( bstr );
// returns 0
 
bstr = '1000000000000000000000000000000000000000000000000000000000000000';
val = fromBits( bstr );
// returns -0
 
bstr = '0111111111111000000000000000000000000000000000000000000000000000';
val = fromBits( bstr );
// returns NaN
 
bstr = '0111111111110000000000000000000000000000000000000000000000000000';
val = fromBits( bstr );
// returns +infinity
 
bstr = '1111111111110000000000000000000000000000000000000000000000000000';
val = fromBits( bstr );
// returns -infinity

Examples

var round = require( 'math-round' );
var pow = require( 'math-power' );
var toBits = require( 'math-float64-bits' );
var fromBits = require( 'math-float64-from-bits' );
 
var frac;
var sign;
var exp;
var b;
var x;
var y;
var i;
 
// Convert random numbers to literal bit representations and then convert them back...
for ( i = 0; i < 100; i++ ) {
    if ( Math.random() < 0.5 ) {
        sign = -1;
    } else {
        sign = 1;
    }
    frac = Math.random() * 10;
    exp = round( Math.random()*100 );
    if ( Math.random() < 0.5 ) {
        exp = -exp;
    }
    x = sign * frac * pow( 2, exp );
    b = toBits( x );
    y = fromBits( b );
    console.log( '%d => %s => %d', x, b, y );
    console.log( x === y );
}

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.